Polarizing plate and liquid crystal display

ABSTRACT

A polarizing plate for a liquid crystal display is provided and includes a first protective film, a polarizer, a second protective film and a light diffusion layer in order. The light diffusion layer is a layer including a translucent resin and translucent particles having a refractive index different from a refractive index of the translucent resin. The internal haze of the light diffusion layer is 45% to 80%.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/280,224 filed on Aug. 21, 2008, which is a U.S. national stageapplication of International Application No. PCT/JP2007/054368 filed onFeb. 28, 2007 and which claims priority to Japanese Application Nos.2006-052473 filed on Feb. 28, 2006, 2006-071427 filed on Mar. 15, 2006,2006-076164 filed on Mar. 20, 2006, 2006-080397 filed on Mar. 23, 2006,2006-081977 filed on Mar. 24, 2006, 2006-088235 filed on Mar. 28, 2006,and 2006-318486 filed on Nov. 27, 2006, the entire contents of all ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a polarizing plate comprising apolarizer interposed between protective layers, and a liquid crystaldisplay using the same.

BACKGROUND ART

A display apparatus using a liquid crystal display (also called a liquidcrystal display panel), an electroluminescence device (classified intoan organic electroluminescence device and an inorganicelectroluminescence device depending on a fluorescent material used),field emission device (FED), an electrophoresis device, etc. can displayan image without providing a space (vacuum basket-like body) where anelectron beam is scanned in a two-dimension behind a display screen,like a cathode ray tube (CRT). Accordingly, such a display apparatus hasan advantage of thinness, light weight, low power consumption, etc. overthe CRT. This display apparatus is also called a flat panel display fromits feature.

The display apparatus using the liquid crystal display, the EL device orthe FED device has spread to replace the CRT in various fields includingOA equipments such as notebook PCs, monitors for PC and so on, mobileterminals, televisions, etc. because of the advantage over the CRT. Thereplacement of the CRT with the flat panel display is based ontechnological innovation in improvement of image quality such as spreadof viewing angle or spread of an area of display color reproducibilityof the liquid crystal display or the EL device. In addition, in recentyears, display quality of moving pictures has been improved asmultimedia and Internet have widely spread. In addition, there appearnew fields including electronic paper or large scaled informationdisplay for public interests or advertisement, which can not be realizedby the CRT.

A liquid crystal display comprises a liquid crystal cell, a drivingcircuit that applies a display signal voltage to the liquid crystalcell, a backlight (a back light source), and a signal control systemthat transmits an input image signal to the driving circuit, which arealso collectively called a liquid crystal module.

The liquid crystal cell includes liquid crystal molecules, twosubstrates that seal and hold the liquid crystal molecules, andelectrode layers that apply a voltage to the liquid crystal molecules. Apolarizing plate is disposed in the outside of the liquid crystal cell.The polarizing plate comprises a protective layer and a polarizer madeof a polyvinyl alcohol film. Specifically, the polarizing plate isobtained by dyeing the polarizer with iodine, expands the dyedpolarizer, and stacking the protective layer on both sides of theexpanded polarizer. In case of a transmission type liquid crystaldisplay, this polarizing plate is attached to both sides of the liquidcrystal cell, and one or more optical compensation sheets may be furtherprovided. In addition, in case of a reflection type liquid crystaldisplay, a reflecting plate, a liquid crystal cell, one or more opticalcompensation sheets, and a polarizing plate are typically arranged inorder.

The liquid crystal cell performs ON/OFF display according to alignmentconditions of the liquid crystal molecules. For the liquid crystal cell,there have been proposed display modes such as TN (Twisted Nematic), IPS(In-Plane Switching), OCB (Optically Compensatory Bend), VA (VerticallyAligned), and ECB (Electrically Controller Birefringence) modes, whichcan be applied to both of the transmission type liquid crystal displayand the reflection type liquid crystal display.

An optical compensation film is used to alleviate image coloring orextend a viewing angle in liquid crystal displays. An expansiblebirefringent polymer film has been used as the optical compensationfilm. Alternatively, in addition to the optical compensation filmcomprising the expansible birefringent polymer film, there has beenproposed to use an optical compensation film having an opticalcompensation layer formed of low molecule or high molecule liquidcrystals on a transparent support. Since the liquid crystal moleculeshave various forms of alignment, use of the liquid crystal moleculesallows realization of optical properties which can not be obtained bythe conventional expansible birefringent polymer film. In addition,there has been proposed a structure that has both of functions of aprotective layer and an optical compensation film by addingbirefringence to the protective layer of a polarizing plate.

An optical property of an optical compensation film depends on anoptical property of a liquid crystal cell, specifically, a display mode.Use of liquid crystal molecules allow manufacture of opticalcompensation films having various optical properties corresponding todifferent display modes of the liquid crystal cell. There have beenalready proposed optical compensation films using liquid crystalmolecules corresponding to various display modes.

For example, an optical compensation film for the TN type liquid crystalcell improves a viewing angle characteristic of contrast by preventionof light leakage in an inclined direction in black color display bymaking an optical compensation of a tilted alignment state for asubstrate while restoring a twisted structure of liquid crystalmolecules by application of a voltage (see JP-A-6-214116 andJP-A-8-50206). An optical compensation film for parallel alignment makesan optical compensation of liquid crystal molecules aligned in parallelto a substrate and improves a viewing angle characteristic ofperpendicular transmittance of a polarizing plate in black color displayunder application of no voltage (see Japanese Patent No. 3342417).

However, even when an optical compensation film made by hybrid-aligningdiscotic liquid crystal compounds uniformly is used, it is verydifficult to fully compensate a liquid crystal cell optically. Forexample, when the TN type liquid crystal cell is observed from aninclined direction, there occurs a gray scale inversion effect thattransmittance in each gray scale is inverted. As one of methods forpreventing the gray scale inversion effect, there has been known amethod for limiting a range of a tilt angle of liquid crystal moleculesin a liquid crystal cell (see “Technical Report of IEICE”, EID 2001-108,p. 47-52).

In addition, under progress of improvement of display quality of liquidcrystal displays, as one of problems of viewing angle characteristics, aproblem of a difference between a γ characteristic in front viewing anda γ characteristic in oblique viewing, that is, a problem of dependencyof a γ characteristic on a viewing angle, has issued at present. Here,the γ characteristic refers to dependency of display luminance on a grayscale. Since the difference between the γ characteristic in frontviewing and the γ characteristic in oblique viewing means that the grayscale depends on a viewing direction, there may occur a particularproblem in case of display of photographs and the like or TVbroadcasting. There has been proposed various liquid crystal displayswith an improved viewing angle characteristic of the γ characteristic.For example, Patent Document 4 discloses a liquid crystal display of anormally black mode with improved dependency of a γ characteristic on aviewing angle. In addition, in an ECB mode with high transmittance andhigh response speed, there is a need to improve a viewing anglecharacteristic by lessening dependency of a γ characteristic on aviewing angle.

On the other hand, although the above-mentioned methods improve theviewing angle characteristic, there occurs a problem of contraction of apolarizing plate and light leakage at a circumference of the polarizingplate under severe use environments, for example, high temperature orhigh humidity environments.

In order to overcome the problem related to durability of the polarizingplate, JP-A-7-191217 and EP 911656 disclose a technique in which anoptical compensation sheet made by applying an optically anisotropiclayer made of a discotic (disk-like) compound on a transparent supportis directly used as a polarizing plate protection film withoutincreasing thickness of a liquid crystal display.

On the other hand, there has been proposed a technique for overcomingthe light leakage problem by properly selecting an adhesive material ofthe polarizing plate (see JP-A-2004-216359).

In addition, in order to overcome the durability problem,JP-A-2001-264538 discloses a technique in which the product of anphotoelastic coefficient of an optical compensation sheet and anelasticity coefficient of an adhesive layer is set to be less than1.2×10⁻⁵, JP-A-2001-272542 discloses a technique in which an elasticitycoefficient of an adhesive layer is set to be less than 0.06 MPa,JP-A-2002-122739 discloses a technique in which the product of a linearexpansion coefficient of a polarizing plate protection layer and anelasticity coefficient of an adhesive layer is set to be less than1.0×10⁻⁵ (° C.⁻¹·MPa), and Patent Document 11 discloses a technique inwhich the product of an photoelastic coefficient of a polarizing plateprotection layer and an elasticity coefficient of an adhesive layer isset to be less than 8.0×10⁻¹² (m²/N·MPa).

DISCLOSURE OF THE INVENTION

An object of an illustrative, non-limiting embodiment of the presentinvention is to provide a liquid crystal display having highly improvedgray scale inversion by improving a viewing angle characteristic with asimple configuration, particularly, an ECB type or IPS type liquidcrystal display of a parallel alignment type without a twisted structureof a liquid crystal layer and a TN type liquid crystal display with atwisted structure of a liquid crystal layer.

Another object of an illustrative, non-limiting embodiment of thepresent invention is to provide a liquid crystal display with improvedreliability under severe environments.

The above-mentioned objects can be achieved by the following means.

(1) A polarizing plate comprising: a first protective film; a polarizer;a second protective film; and a light diffusion layer in this order,wherein the light diffusion layer comprises a translucent resin andtranslucent particles having a refractive index different from that ofthe translucent resin, and the light diffusion layer has an internalhaze of 45 to 80%.(2) The polarizing plate according to (1), further comprising an opticalcompensation layer.(3) The polarizing plate according to (1) or (2), wherein the lightdiffusion layer has such a scattering light profile measured by agoniophotometer that a intensity of scattering light having an emissionangel of 30° with respect to scattering light having an emission angleof 0° falls within a range of 0.05 to 0.3%.(4) The polarizing plate according to any one of (1) to (3), which hasan absorption axis parallel or perpendicular to one side of thepolarizing plate.

(5) The polarizing plate according to any one of (1) to (3), which hasan absorption axis having an angle of 5 to 40° with one side of thepolarizing plate.

(6) A liquid crystal display comprising:

a liquid crystal cell comprising a pair of substrates disposed oppositeto each other, one of the pair of substrates having an electrode on oneside thereof, and a liquid crystal layer between the pair of substrates;and

a polarizing plate disposed on at least one outer side of the liquidcrystal cell, the polarizing plate comprising a first protective film; apolarizer, a second protective film, and a light diffusion layer in thisorder, wherein the light diffusion layer comprises a translucent resinand translucent particles having a refractive index different from thatof the translucent resin, and the light diffusion layer has an internalhaze of 45 to 80%.

(7) The liquid crystal display according to (6), wherein the liquidcrystal layer includes a nematic liquid crystal material alignedsubstantially parallel to surfaces of the pair of substrates underapplication of no voltage.

(8) The liquid crystal display according to (6) or (7), wherein thepolarizing plate further comprises an optical compensation layer.

(9) The liquid crystal display according to any one of (6) to (8),wherein the polarizer has an absorption axis parallel or perpendicularto a horizontal direction of a screen of the liquid crystal display.

(10) A liquid crystal display comprising:

a pair of substrates disposed opposite to each other, one of the pair ofsubstrates having an electrode on one side thereof;

a liquid crystal layer between the pair of substrates, the liquidcrystal layer including liquid crystal molecules alighted by alignmentaxes of opposite surfaces of the pair of substrates; and

a pair of polarizing plates, each comprising an adhesive layer, anoptical compensation sheet, a polarizer and a protective layer in thisorder, the liquid crystal cell being between the pair of polarizingplates, wherein at least one of the pair of polarizing plates has anabsorption axis having an angle of 5° and 40° with respect to one of ahorizontal direction and a vertical direction of a screen of the liquidcrystal display.

(11) The liquid crystal display according to (10), wherein at least oneof the polarizing plates further comprises a light diffusion layer, thelight diffusion layer comprises a translucent resin and translucentparticles having a refractive index different from that of thetranslucent resin, and the light diffusion layer has an internal haze of45 to 80%.(12) A liquid crystal display comprising:

a pair of first and second substrate disposed opposite to each other,one of the pair of first and second substrates having a transparentelectrode on one side thereof;

a liquid crystal layer between the pair of first and second substrates,the liquid crystal layer including liquid crystal molecules alignedsubstantially parallel to surfaces of the pair of first and secondsubstrates under application of no voltage, the liquid crystal moleculeshaving a twist angle of 45° or less between the first and secondsubstrates; and

a plurality of pixels including a plurality of electrodes that apply avoltage to the liquid crystal layer, wherein

-   -   each of the pixels includes a first sub pixel and a second sub        pixel which apply different voltages to the liquid crystal        layer,    -   each of the pixels is capable of representing a 0 to n gray        scales, n being an integer of 1 or more and higher n        representing a gray scale having higher luminance, and    -   each of the pixels satisfies formula |V1(k)−V2(k)|>0 when the        each of the pixels represent at least k gray scale, wherein        V1(k) and V2(k) represents effective voltages by Volt applied to        the liquid crystal layer of the first and second sub pixels,        respectively, and k satisfies 0<k≦n−1, and

wherein the liquid crystal display displays an image in a normally whitemode.

(13) The liquid crystal cell according to (12), further comprising apolarizing plate disposed on at least one outer side of the liquidcrystal layer, the polarizing plate comprising a first protective film;a polarizer, a second protective film, and a light diffusion layer inthis order, wherein the light diffusion layer comprises a translucentresin and translucent particles having a refractive index different fromthat of the translucent resin, and the light diffusion layer has aninternal haze of 45 to 80%.(14) A liquid crystal display comprising:

a pair of first and second substrate disposed opposite to each other,one of the pair of first and second substrates having a transparentelectrode on one side thereof;

a liquid crystal layer between the pair of first and second substrates,the liquid crystal layer including liquid crystal molecules alignedsubstantially parallel to surfaces of the pair of first and secondsubstrates under application of no voltage, the liquid crystal moleculeshaving a twist angle of substantially 90° between the first and secondsubstrates; and

a plurality of pixels including a plurality of electrodes that apply avoltage to the liquid crystal layer, wherein

-   -   each of the pixels includes a first sub pixel and a second sub        pixel which apply different voltages to the liquid crystal        layer,    -   each of the pixels is capable of representing a 0 to n gray        scales, n being an integer of 1 or more and higher n        representing a gray scale having higher luminance, and    -   each of the pixels satisfies formula |V1(k)−V2(k)|>0 when the        each of the pixels represent at least k gray scale, wherein        V1(k) and V2(k) represents effective voltages by Volt applied to        the liquid crystal layer of the first and second sub pixels,        respectively, and k satisfies 0<k≦n−1, and

wherein the liquid crystal display displays an image in a normally whitemode.

(15) The liquid crystal cell according to (14), further comprising apolarizing plate disposed on at least one outer side of the liquidcrystal layer, the polarizing plate comprising a first protective film;a polarizer, a second protective film, and a light diffusion layer inthis order, wherein the light diffusion layer comprises a translucentresin and translucent particles having a refractive index different fromthat of the translucent resin, and the light diffusion layer has aninternal haze of 45 to 80%.(16) A liquid crystal display comprising:

a pair of polarizing plates, each comprising a polarizer and atransparent layer, transmission axes of the pair of polarizing platesbeing perpendicular to each other; and

a liquid crystal panel between the pair of polarizing plates, whereinthe liquid crystal panel comprises a pair of substrates disposedopposite to each other, one of the pair of substrates having anelectrode on one side thereof, a liquid crystal layer including liquidcrystal molecules alighted by alignment axes of opposite surfaces of thepair of substrates, and a pair of optically anisotropic layers, theliquid crystal layer being between the pair of optically anisotropiclayers

wherein the liquid crystal panel has a double symmetrical axis withrespect to a cubic structure defined by: upper and lower alignmentcontrol directions of the liquid crystal layer which are defined by thealignment axes of opposite surfaces of the pair of substrates; andalignment control directions of the pair of optically anisotropiclayers, the double symmetrical axis being parallel to the surfaces ofthe pair of substrates, a transmission axis of one of the pair ofpolarizing plates is parallel to the double symmetrical axis, and atransmission axis of the other of the pair of polarizing plates isperpendicular to the double symmetrical axis, and

wherein the transparent layer between the liquid crystal layer and thepolarizer is a biaxial retardation layer, the biaxial retardation layerhaving: an in-plane retardation of 250 to 300 nm; an NZ value of 0.1 to0.4; and an in-plane retardation axis perpendicular to an absorptionaxis of the polarizer closer to the biaxial retardation layer.

(17) The liquid crystal display according to (16), wherein at least oneof the polarizing plates further comprises a light diffusion layer,wherein the light diffusion layer comprises a translucent resin andtranslucent particles having a refractive index different from that ofthe translucent resin, and the light diffusion layer has an internalhaze of 45 to 80%.(18) A liquid crystal display comprising:

a pair of first and second substrate disposed opposite to each other,one of the pair of first and second substrates having a transparentelectrode on one side thereof;

a liquid crystal layer between the pair of first and second substrates,the liquid crystal layer including liquid crystal molecules alignedsubstantially parallel to surfaces of the first and second substratesunder application of no voltage, the liquid crystal molecules having atwist angle of 45° or less between the first and second substrates;

a pair of first and second polarizing plates having absorption axesperpendicular to each other, the liquid crystal layer being between thepair of first and second polarizing plates;

at least one first retardation layer disposed at least one of betweenthe at least one first polarizing plate and the liquid crystal layer andbetween the second polarizing plate and the liquid crystal layer; and

a second retardation layer disposed between the first polarizing plateand the liquid crystal layer, the second retardation layer including acompound having a discotic structural unit,

wherein the at least one first retardation layer satisfies formulae:0 nm<Re(550)<70 nm0 nm<Rth(550)<330 nmwherein Re(550) represents a summation of in-plane retardations of theat least first retardation layer at the wavelength of 550 nm, andRth(550) represents a summation of thickness-direction retardations ofthe at least first retardation layer at the wavelength of 550 nm.(19) The liquid crystal display according to (18), wherein at least oneof the first and second polarizing plates further comprises a lightdiffusion layer, wherein the light diffusion layer comprises atranslucent resin and translucent particles having a refractive indexdifferent from that of the translucent resin, and the light diffusionlayer has an internal haze of 45 to 80%.(20) The liquid crystal display according to (18), further comprising aretardation layer disposed between the second polarizing plate and theliquid crystal layer, the retardation layer including a compound havinga discotic structural unit, wherein the at least one first retardationlayer satisfies formula: 0 nm<Rth(550)<200 nm(21) The liquid crystal display according to (19), wherein at least oneof the first and second polarizing plates further comprises a lightdiffusion layer, wherein the light diffusion layer comprises atranslucent resin and translucent particles having a refractive indexdifferent from that of the translucent resin, and the light diffusionlayer has an internal haze of 45 to 80%.(22) A liquid crystal display comprising:

a pair of substrates disposed opposite to each other, one of the pair ofsubstrates having an electrode on one side thereof;

a liquid crystal layer between the pair of substrates, the liquidcrystal layer including liquid crystal molecules alighted by alignmentaxes of opposite surfaces of the pair of substrates;

a pair of polarizing plates, each comprising a polarizer and aprotective film, the liquid crystal layer being between the pair ofpolarizing plates; and

an optically anisotropic layer between the liquid crystal layer and atleast one of the pair of polarizing plates, the optically anisotropiclayer including a liquid crystal compound aligned by an alignment axisand fixed,

wherein an absorption axis of the polarizer is parallel or perpendicularto a horizontal direction of a screen of the liquid crystal display, atleast one of the alignment axes of surfaces of the pair of substratesintersects an alignment control direction of the optically anisotropiclayer by 10 to 35°, and the protective film satisfies formula:Re+2×Rth≦280wherein Re represents an in-plane retardation, and Rth represents athickness-direction retardation.(23) The liquid crystal display according to (22), wherein at least oneof the polarizing plates further comprises a light diffusion layer,wherein the light diffusion layer comprises a translucent resin andtranslucent particles having a refractive index different from that ofthe translucent resin, and the light diffusion layer has an internalhaze of 45 to 80%.(24) The liquid crystal display according to any one of (6) to (9),which is an ECB liquid crystal display.(25) The liquid crystal display according to any one of (6) to (9),which is a TN liquid crystal display.(26) The liquid crystal display according to any one of (6) to (9),which is an IPS liquid crystal display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an example of an ECB type liquidcrystal display according to an exemplary embodiment of the invention.

FIG. 2 is a schematic view showing an example of an ECB type liquidcrystal display according to an exemplary embodiment of the invention.

FIG. 3 is a schematic view showing an example of a TN type liquidcrystal display according to an exemplary embodiment of the invention.

FIG. 4 is a schematic view showing an example of an IPS type liquidcrystal display according to an exemplary embodiment of the invention.

FIG. 5 is a schematic sectional view showing an example of an IPS typeliquid crystal display according to an exemplary embodiment of theinvention.

FIG. 6 is a schematic sectional view showing an example of an IPS typeliquid crystal display according to an exemplary embodiment of theinvention.

FIG. 7 is a schematic view showing a TN type liquid crystal displayusing a polarizing plate according to an exemplary embodiment of theinvention.

FIG. 8A is a view showing a relationship between an absorption axisdirection and sides of upper and lower polarizing plates in a liquidcrystal display according to an exemplary embodiment of the invention,and FIG. 8B is a view showing a relationship therebetween in a liquidcrystal display in the background art.

FIG. 9 is a graph that plots transmittance (%) of leakage light withrespect to an angle between absorption axis of a polarizing plate and anend line of the polarizing plate.

FIG. 10 is a schematic view showing a configuration of a liquid crystaldisplay 100 according to an exemplary embodiment of the invention.

FIG. 11 is a schematic plan view showing an exemplary configuration ofone pixel 350 of a liquid crystal display 100.

FIG. 12 is a schematic plan view showing an exemplary configuration ofan electrode structure of a pixel 350′ of a liquid crystal display 100′in the background art.

FIG. 13 is a graph showing a relationship between gray scales in frontand inclined directions of liquid crystal displays according to Example4 and Comparative example 4.

FIG. 14 is a schematic view showing an example of a liquid crystaldisplay according to an exemplary embodiment of the invention.

FIG. 15 is a schematic view showing an example of a liquid crystaldisplay in the background art.

FIG. 16 is a schematic view used to explain double symmetry of a liquidcrystal panel.

FIG. 17 is a schematic view used to explain double symmetry of a liquidcrystal panel.

FIG. 18 is a schematic view used to explain double symmetry of a liquidcrystal panel.

FIG. 19 is a view showing that a locus of a polarization state of lightincident into a liquid crystal display is plotted on a Poincare sphereaccording to an exemplary embodiment of the invention.

FIG. 20 is a view showing that a locus of a polarization state of lightincident into a liquid crystal display is plotted on a Poincare sphereaccording to an exemplary embodiment of the invention.

FIG. 21 is a view showing that a locus of a polarization state of lightincident into a liquid crystal display is plotted on a Poincare sphereaccording to an exemplary embodiment of the invention.

FIG. 22 is a view showing that a locus of a polarization state of lightincident into a liquid crystal display is plotted on a Poincare sphereaccording to an exemplary embodiment of the invention.

FIG. 23 is a view showing a contrast viewing angle characteristicaccording to Comparative example 5.

FIG. 24 is a view showing a contrast viewing angle characteristicaccording to Example 5.

FIG. 25 is a schematic sectional view showing an exemplary configurationof a liquid crystal display according to an exemplary embodiment of theinvention.

FIG. 26 is a schematic sectional view showing an exemplary configurationof a liquid crystal display according to an exemplary embodiment of theinvention.

FIG. 27 is a schematic sectional view showing an exemplary configurationof a liquid crystal display according to an exemplary embodiment of theinvention.

FIG. 28 is a schematic sectional view showing an exemplary configurationof a liquid crystal display according to an exemplary embodiment of theinvention.

FIG. 29 is a graph showing a relationship between transmittance (inaverage direction of polar angle 80° vertical and horizontal directions)in black image display of a liquid crystal display having the sameconfiguration as Example 6-1 and Rth of a first retardation layer(where, Re=36.6 nm).

FIG. 30 is a graph showing a relationship between transmittance (inaverage direction of polar angle 80° vertical and horizontal directions)in black image display of a liquid crystal display having the sameconfiguration as Example 6-2 and Rth of a first retardation layer(where, Re=3.2 nm).

FIG. 31 is a schematic view showing an example of a liquid crystaldisplay in the background art.

FIG. 32 is a schematic view showing an example of a liquid crystaldisplay according to an exemplary embodiment of the invention.

FIGS. 33A to 33C are views showing alignment control directions of aliquid crystal layer 611 and upper and lower optically anisotropiclayers 607 and 614 of a liquid crystal display according to an exemplaryembodiment of the invention when viewed from a display plane side.

FIG. 34 is a schematic view showing an example of a liquid crystaldisplay according to a reference example by 0°-90° attachment.

FIG. 35 is a graph showing a relationship between a width of a CR visualfield of an inclined direction and an equation of “Re+2×Rth≦280”.

FIG. 36 is a graph showing a relationship between a width of a CR visualfield of an inclined direction and an equation of “Re+2×Rth≦280”.

Reference sings and numerals are set forth below.

-   1: upper polarizing plate-   11: protective film for upper polarizing plate-   11D: retardation axis of protective film for upper polarizing plate-   12: polarizer of upper polarizing plate-   12D: absorption axis of polarizer of upper polarizing plate-   13: protective film for upper polarizing plate-   13D: retardation axis of protective film for upper polarizing plate-   14: upper optical compensation film-   14RD: alignment direction of upper optical compensation film-   5: upper substrate of liquid crystal cell-   5RD: rubbing direction of upper substrate for liquid crystal    alignment-   6: liquid crystal molecule, liquid crystal layer-   7: lower substrate of liquid crystal cell-   7RD: rubbing direction of lower substrate for liquid crystal    alignment-   24: lower optical compensation film-   24RD: alignment direction of lower optical compensation film-   2: lower polarizing plate-   23: protective film for lower polarizing plate-   23D: retardation axis of protective film for lower polarizing plate-   22: polarizer of lower polarizing plate-   22D: absorption axis of polarizer of lower polarizing plate-   21: protective film for lower polarizing plate-   21D: retardation axis of protective film for lower polarizing plate-   9D: electric field direction-   91: linear electrode-   93: Insulating film-   92: electrode-   80: light source-   TN1: upper polarizing plate-   TN2: absorption axis direction of upper polarizing plate-   TN3: upper optically anisotropic layer-   TN4: alignment control direction of upper optically anisotropic    layer-   TN5: upper electrode substrate of liquid crystal cell-   TN6: alignment control direction of upper substrate-   TN7: liquid crystal layer-   TN8: lower electrode substrate of liquid crystal cell-   TN9: alignment control direction of lower substrate-   TN10: lower optically anisotropic layer-   TN11: alignment control direction of lower optically anisotropic    layer-   TN12: lower polarizing plate-   TN13: absorption axis direction of lower polarizing plate-   301: upper protective film for upper polarizing plate-   302: retardation axis of upper protective film-   303: upper polarizer-   304: absorption axis of upper polarizer-   305: lower protective film for upper polarizing plate-   306: retardation axis of lower protective film-   307: upper optical compensation film-   308: alignment control direction (rubbing direction) of upper    optical compensation film-   309: upper substrate of liquid crystal cell-   310: alignment control direction (rubbing direction) of upper    substrate for liquid crystal alignment-   311: liquid crystal molecule-   312: lower substrate of liquid crystal cell-   313: alignment control direction (rubbing direction) of lower    substrate for liquid crystal alignment-   314: lower optical compensation film-   315: alignment control direction (rubbing direction) of lower    optical compensation film-   316: upper protective film for lower polarizing plate-   317: retardation axis of upper protective film-   318: lower polarizing plate-   319: absorption axis of lower polarizing plate-   320: lower protective film for lower polarizing plate-   321: retardation axis of lower protective film-   350, 350′: pixel-   350 a, 350 b: sub pixel-   352: scan line-   345 a, 345 b, 354′: signal line-   356 a, 356 b, 356′: TFT-   358 a, 358 b: sub pixel electrode-   358′: pixel electrode-   100, 100′: liquid crystal display-   401: polarizer of upper polarizing plate-   402: transmission axis of polarizer of upper polarizing plate-   403: transparent layer of upper polarizing plate-   404: retardation axis of transparent layer of upper polarizing plate-   405 a: upper first optically anisotropic layer-   406 a: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of upper first    optically anisotropic layer-   405 b: upper second optically anisotropic layer-   406 b: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of upper second    optically anisotropic layer-   407: upper substrate of liquid crystal cell-   408: rubbing direction (alignment axis) of upper substrate for    liquid crystal alignment-   409: liquid crystal molecule (liquid crystal layer)-   410: lower substrate of liquid crystal cell-   411: rubbing direction (alignment axis) of lower substrate for    liquid crystal alignment-   412 a: lower first optically anisotropic layer-   413 a: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of lower first    optically anisotropic layer-   412 b: lower second optically anisotropic layer-   413 b: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of lower second    optically anisotropic layer-   414: transparent layer of lower polarizing plate-   415: retardation axis of transparent layer of lower polarizing plate-   416: polarizer of lower polarizing plate-   417: transmission axis of polarizer of lower polarizing plate-   451: polarizer of upper polarizing plate-   452: absorption axis of polarizer of upper polarizing plate-   453: transparent layer of upper polarizing plate-   454: retardation axis of transparent layer of upper polarizing plate-   455: upper optically anisotropic layer-   456: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of upper    optically anisotropic layer-   457: upper substrate of liquid crystal cell-   458: rubbing direction (alignment axis) of upper substrate for    liquid crystal alignment-   459: liquid crystal molecule (liquid crystal layer)-   460: lower substrate of liquid crystal cell-   461: rubbing direction (alignment axis) of lower substrate for    liquid crystal alignment-   462: lower optically anisotropic layer-   463: alignment average direction (alignment control direction) of    molecule symmetrical axis of liquid crystal compound of lower    optically anisotropic layer-   464: transparent layer of lower polarizing plate-   465: retardation axis of transparent layer of lower polarizing plate-   466: polarizer of lower polarizing plate-   467: absorption axis of polarizer of lower polarizing plate-   510, 512: transparent substrate-   514: liquid crystal layer-   516, 518: polarizer (first and second polarizers)-   520, 522: retardation plate (first retardation layer) and protective    layer for polarizing plate-   523: transparent support for polarizing plate protective layer and    optical compensation film-   524, 526: optical compensation film (second retardation layer)    including discotic structural unit-   601: outer protective film for upper polarizing plate-   602: retardation axis of outer protective film for upper polarizing    plate-   603: polarizer of upper polarizing plate-   604: absorption axis of polarizer of upper polarizing plate-   605: protective film on liquid crystal cell side of upper polarizing    plate (support)-   606: retardation axis of protective film on liquid crystal cell side    of upper polarizing plate (support)-   607: upper optically anisotropic layer-   608: rubbing direction (alignment control direction) at support side    of upper optically anisotropic layer for liquid crystal alignment-   609: upper substrate of liquid crystal cell-   610: rubbing direction (alignment control direction) of upper    substrate for liquid crystal alignment-   611: liquid crystal molecule (liquid crystal layer)-   612: rubbing direction (alignment control direction) of lower    substrate for liquid crystal alignment-   613: lower substrate of liquid crystal cell-   614: lower optically anisotropic layer-   615: rubbing direction (alignment control direction) at support side    of lower optically anisotropic layer for liquid crystal alignment-   616: protective film on liquid crystal cell side of lower polarizing    plate (support)-   617: retardation axis of protective film on liquid crystal cell side    of lower polarizing plate (support)-   618: polarizer for lower polarizing plate-   619: absorption axis of polarizer for lower polarizing plate-   620: outer protective film for lower polarizing plate-   621: retardation axis of outer protective film for lower polarizing    plate-   θ: intersection angle between alignment control direction of liquid    crystal layer and alignment control direction of optically    anisotropic layer-   φ: angle between alignment control direction of pair of upper and    lower optically anisotropic layers

DETAILED DESCRIPTION OF THE INVENTION

According to an exemplary embodiment of the invention, a polarizingplate having a function of optically compensating a liquid crystal cellwith the same configuration as the liquid crystal display in thebackground art can be provided by controlling material of a polarizingplate protective film, a light diffusion layer, a surface film and aliquid crystal cell and a manufacturing method thereof. In addition,when the manufacture polarizing plate is attached to ECB type, IPS typeand TN type liquid crystal cells, a viewing angle as well as displayquality can be remarkably improved. In addition, since there is no needfor processes of stacking one or more retardation films and polarizingplates while controlling their angles, it is possible to manufacture thepolarizing plate in a roll-to-roll manner. In addition, according to anexemplary embodiment of the invention, there can be provided apolarizing plate which is capable of not only providing a polarizationfunction but also extending an viewing angle of a liquid crystaldisplay, reducing gray scale inversion, preventing imprint of externallight, and being simply manufactured.

According to an aspect of the invention, there is provided a liquidcrystal display with high display quality without light leakage whichoccurs when the liquid crystal display is heated.

In addition, according to another aspect of the invention, there isprovided a normally white mode liquid crystal display with an excellentviewing angle characteristic with reduced dependency of γ characteristicon a viewing angle. Particularly, according to still another aspect ofthe invention, there is provided a normally white mode liquid crystaldisplay with high viewing angle contrast with reduced light leakage inan inclined direction in black display as well as with an excellentviewing angle characteristic reduced dependency of γ characteristic on aviewing angle.

Terms used in the specification will be first described.

(Description of Terms)

(Retardation, Re, Rth)

In the specification, Re(λ) and Rth(λ) represent retardation in planeand retardation in thickness for a wavelength λ, respectively. Re(λ) ismeasured when light having a wavelength of λ, nm is incident in a normaldirection of a film in “KOBRA 21ADH” or “KOBRA 21WR” {available from OjiScientific Instruments. Co., Ltd.}.

If a measured film is represented by a one or two-axis refractive indexellipsoid, Rth(λ) is calculated according to the following method.

When Re(λ) is measured at 6 points when a wavelength of λ nm is incidentin a direction inclined by 10° step from a normal direction of a film upto 50° in one side, with a retardation axis in plane (determined by“KOBRA 21ADH” or “KOBRA 21WR”) as an inclined axis (rotation axis) (withany direction in a film plane as a rotation axis if there is noretardation axis), Rth(λ) is calculated by “KOBRA 21ADH” or “KOBRA21WR,” based on the measured retardation values, a presumed value of anaverage refractive index and an inputted film thickness value.

In the above, if the film has a direction in which the retardation valueis zero at an inclined angle from the normal direction, with theretardation axis in plane as the rotation axis, after signs ofretardation values are changed to be negative at an angle larger thanthe inclined angle, Rth(λ) is calculated by “KOBRA 21ADH” or “KOBRA21WR.”

In addition, when retardation values are measured in any two directions,with the retardation axis as the inclined axis (rotation axis) with anydirection in the film plane as the rotation axis if there is noretardation axis), Rth(λ) may be calculated, based on the measuredretardation values, a presumed value of an average refractive index andan inputted film thickness value, according to the following equations(1) and (2).

$\begin{matrix}{{{Re}(\theta)} = {\left\lbrack {{nx} - \frac{\left( {{ny} \times {nz}} \right)}{\sqrt{\begin{matrix}{\left\{ {{ny}\;{\sin\left( {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right)}} \right\}^{2} +} \\\left\{ {{nz}\;{\cos\left( {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right)}} \right\}^{2}\end{matrix}}}} \right\rbrack\frac{d}{\cos\left\{ {\sin^{- 1}\left( \frac{\sin\left( {- \theta} \right)}{nx} \right)} \right\}}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

In the above equation (1), Re(θ) represents a retardation value in adirection inclined by a θ angle from a normal direction, nx represents arefractive index in a retardation axis direction in plane, ny representsa refractive index in a direction perpendicular to nx in plane, nzrepresents a refractive index in a direction perpendicular to nx and ny,and d represents a film thickness.Rth=((nx+ny)/2−nz)×d  Equation (2)

If a measured film can not be represented by a one or two-axisrefractive index ellipsoid, that is, if the measured film is a filmhaving no optic axis, Rth(λ) is calculated according to the followingmethod.

When Re(λ) is measured at 11 points when a wavelength of λ nm isincident in a direction inclined by 10° step from a film normaldirection up to +50°, with a retardation axis in plane (determined by“KOBRA 21ADH” or “KOBRA 21WR”) as an inclined axis (rotation axis),Rth(λ) is calculated by “KOBRA 21ADH” or “KOBRA 21WR,” based on themeasured retardation values, a presumed value of an average refractiveindex and an inputted film thickness value.

In the above measurement, the presumed value of the average refractiveindex may use values listed in “Polymer Handbook” (JOHN WILEY&SONS, INC)and catalogs of various optical films. If the average refractive indexis not known, it may be measured using An Abbe refractometer. Averagerefractive indexes of main optical films are exemplified as follows:

Celluloseacylate (1.48), cycloolefin polymer (1.52), polycarbonate(1.59), polymethylmethacrylate (1.49), polystyrene (1.59)

When presumed values of these average refractive indexes and filmthickness are inputted, “KOBRA 21ADH” or “KOBRA 21WR” calculates nx, nyand nz. Also, using the calculated nx, ny and nz, it is calculated thatNz=(nx−nz)/(nx−ny).

(Molecule Alignment Axis)

A molecule alignment axis is calculated by an auto birefractometer{“KOBRA 21ADH” available from Oji Scientific Instruments. Co., Ltd.}using a phase difference obtained when a sample of 70 mm×100 mm iscontrolled with its humidity for two hours at 25° C. and 65% RH.

(Transmittance)

A transmittance of visible light (615 nm) for a sample of 20 mm×70 mm ismeasured at 25° C. and 60% RH by a transparency meter (“AKA phototubecolorimeter” available from KOTAKI Co., Ltd.).

(Spectral Property)

A transmittance of light having a wavelength of 300 to 450 nm for asample of 13 mm×40 mm is measured at 25° C. and 60% RH by aspectrophotometer (“U-3210” available from HITACHI Co., Ltd.). Aninclination width is obtained using a wavelength of 72% to 5%. Athreshold wavelength is indicated by a wavelength of {(inclinationwidth/2)+5%}. An absorption edge is indicated by a wavelength of atransmittance of 0.4%. Based on these factors, a transmittance of lighthaving a wavelength of 380 nm and 350 nm is evaluated.

In the specification, in an angle, “+” means a counterclockwisedirection and “−” means a clockwise direction. An absolute value 0°direction in an angle direction means a 3 o'clock direction (rightdirection of a screen) when upward and downward directions of a liquidcrystal display are taken as 12 and 6 o'clock directions. In addition,“retardation axis” means a direction giving the maximum refractiveindex. “Visible light region” means a range of wavelength of 380 nm to780 nm. In addition, a measurement wavelength of a refractive indexrefers to a value at λ=550 nm in the visible light region if notmentioned otherwise.

For an angle between axes or between direction, “parallel”“perpendicular”, “45°”, etc. means “substantially parallel”“substantially perpendicular”, “substantially 45°”, etc., but not in thestrict sense. That is, slight deviation within a range in which apurpose can be achieved is permitted. For example, “parallel” means thatan intersection angle is substantially 0°, for example, −10° to 10°,preferably, −5° to 5°, more preferably, −3° to 3°. “perpendicular” meansthat an intersection angle is substantially 90°, for example, 80° to100°, preferably, 85° to 95°, more preferably, 87° to 93°. “45°” meansthat an intersection angle is substantially 45°, for example, −35° to55°, preferably, 40° to 50°, more preferably, 42° to 48°.

In the specification, “polarizing plate” is intended to include both ofa long polarizing plate and a polarizing plate cut with a size suitablefor a liquid crystal display (in the specification, “cut” is intended toinclude “punching”, “trimming”, etc.) if not mentioned otherwise. In thespecification, although “polarizer” and “polarizing plate” aredistinguishably used, “polarizing plate” means a stacked structure inwhich a protective film to protect “polarizer” is stacked on at leastone side of “polarizer”. In case where the polarizing plate includes anoptical compensation film, the protective film may be used as theoptical compensation film. In case where the optical compensation filmcomprises an optically anisotropic layer having liquid crystal moleculesstacked in a support, the protective film may be used as the support ofthe optical compensation film. In addition, the polarizing plate of theinvention may include a support. In addition, in some cases, “opticalcompensation film” may have the same meaning as the opticallyanisotropic layer.

Hereinafter, exemplary embodiments of the invention will be described.

<Liquid Crystal Display>

(Configuration of Liquid Crystal Display)

A liquid crystal display according to one aspect of the inventionincludes a pair of substrates disposed opposite to each other, one ofwhich has an electrode, a liquid crystal cell that is interposed betweenthe pair of substrates and comprises a liquid crystal layer including anematic liquid crystal material aligned substantially parallel tosurfaces of the pair of substrates under application of no voltage, anda polarizing plate arranged on at least one outer side of the liquidcrystal cell. In the liquid crystal display, the polarizing plateincludes a first protective film, a second protective film and a lightdiffusion layer in order. The light diffusion layer is a layercontaining translucent resin and translucent particles having arefractive index different from a refractive index of the translucentresin. In addition, internal haze of the light diffusion layer is 45% to80%.

It is preferable that a TN type liquid crystal display, an ECB typeliquid crystal display or an IPS type liquid crystal display is used asthe liquid crystal display of the invention.

The ECB type liquid crystal display has a normally white display modewhere a white image is displayed under application of no voltage, and atransmittance is decreased and a black image is displayed accordinglyunder application of a high voltage. The black image is displayed when aRe value of an optical compensation film becomes equal to a retardationvalue of a liquid crystal layer under application of a voltage. Withthis configuration, an image of high contrast can be obtained over awide range, and there occurs no gray scale inversion in a halftonedisplay region.

In addition, in case where the ECB type liquid crystal display is usedas the liquid crystal display of the invention, an intersection anglebetween an absorption axis of the polarizer and an alignment treatmentdirection of the liquid crystal layer falls within a range ofpreferably, 40 to 50°, more preferably, 45°.

The TN type liquid crystal display has a normally white display modewhere a white image is displayed under application of no voltage, and atransmittance is decreased and a black image is displayed accordinglyunder application of a high voltage. The black image is displayed when aRe value of an optical compensation film becomes equal to a retardationvalue of a liquid crystal layer under application of a voltage. Withthis configuration, an image of high contrast can be obtained over awide range. In case where an absorption axis of a polarizer is inclinedby 45° or −45° with respect to a horizontal direction of a screen, anintersection angle between the absorption axis of the polarizer and analignment treatment direction of the liquid crystal layer falls within arange of, preferably, −10 to 10°, more preferably, 0°. In addition, incase where the polarizer is in parallel to or is inclined by 90° withrespect to the horizontal direction of the screen, an intersection anglebetween the absorption axis of the polarizer and an alignment treatmentdirection of the liquid crystal layer falls within a range of,preferably, 20 to 70°.

In addition, the IPS type liquid crystal display has a normally blackdisplay mode where a black image is displayed under application of novoltage, and a transmittance is increased and a white and black image isdisplayed accordingly under application of a high voltage. A viewingangle of the black image can be extended by optimizing Re and Rth valuesof an optical compensation film. With this configuration, in apolarizing plate at a observer side from the liquid crystal cell, anintersection angle between the absorption axis of the polarizer and aninitial alignment treatment direction of the liquid crystal layer fallswithin a range of, preferably, 80 to 100°, more preferably, 90°. In apolarizing plate far away from a observer side with the liquid crystalcell interposed therebetween, an intersection angle between theabsorption axis of the polarizer and an initial alignment treatmentdirection of the liquid crystal layer falls within a range of,preferably, −10 to 10°, more preferably, 0°.

A light diffusion layer is stacked on the second protective film. Thislight diffusion layer has an effect of widening a contrast viewingangle, making change of a color viewing angle small, decreasing grayscale inversion and reducing display spots.

In addition, in the liquid crystal display of the invention, it ispreferable that at least one optical compensation film is interposedbetween the polarizing plate and the liquid crystal layer.

The optical compensation film is not particularly limited, but may haveany configuration as long as it has an optical compensation function.For example, the optical compensation film may be a birefringent polymerfilm or a stacked structure including a transparent support and anoptical compensation layer comprising liquid crystal molecules formed onthe transparent support. In the latter, a transparent protective filmcloser to the liquid crystal layer of the polarizing plate may be usedas a support of the optical compensation film. That is, the polarizingplate may have the optical compensation layer.

It is preferable that the optical compensation film for the TN and ECBtype liquid crystal display is an optical compensation film having adiscotic structural unit. In the invention, it is preferable that analignment control direction of the optical compensation film having thediscotic structural unit is in substantial parallel to the absorptionaxis of the polarizer of the polarizing plate.

In the liquid crystal display of the invention, it is preferable that adisk plane of the discotic structural unit is inclined with respect tothe polarizer (or transparent support plane) and an angle between thedisk plane of the discotic structural unit and the polarizer (ortransparent support plane) is changed in a direction perpendicular to afilm plane of the optical compensation film (that is, thicknessdirection). In this liquid crystal display, it is possible to obtain animage without the contrast viewing angle and gray scale inversion.

The optical compensation film used in the invention may be an opticalcompensation film comprising an expansible film, in addition to anoptical compensation film comprising a compound having an alignedtransparent support and a discotic structural unit formed on thesupport. The optical compensation film has an effect of reducing lightleakage in an inclined direction of black color display for a liquidcrystal display in which the liquid crystal cell of the normally blackdisplay mode where the black image is displayed under application of novoltage has two or more picture element regions, and each of the pictureelement regions has two or more regions having different initialalignment states of molecules of the nematic liquid crystal material, ortwo or more different regions where an alignment direction of moleculesof the nematic liquid crystal material is continuously changed underapplication of a voltage.

In addition, in the liquid crystal display of the invention, it may beconfigured that one pixel of the liquid crystal cell has two or morepicture element regions, and the picture element regions have differentinitial alignment states of liquid crystal molecules or differentalignment directions of liquid crystal molecules that are continuouslychanged under application of a voltage.

Such a configuration is particularly effective for the ECB type liquidcrystal display in which the liquid crystal molecules are inclined withrespect to a substrate normal by the application of voltage. Inaddition, since the liquid crystal molecules are inclined in onedirection, by dividing one pixel into two or more (preferably, 2 or 4 ormore) picture element regions having different initial alignment statesand averaging the picture element regions, luminance and color tune canbe suppressed from being biased.

In addition, the invention relates to a liquid crystal display in whichan absorption axis of a polarizer is in parallel or perpendicular to ahorizontal direction of a screen of the liquid crystal display(hereinafter, this aspect is sometimes referred to as a preferred aspect(I)).

In conventional liquid crystal displays, a polarizing plate iscontracted under severe environments. Particularly, the polarizing plateshows the maximal contraction in a direction in parallel to long andshort side of a screen. When an elastic force such as contraction orexpansion is applied to a film used in such a polarizing plate,retardation is changed. In a configuration where an absorption axis ofthe polarizing plate intersects a generation direction of theretardation by 45°, light transmission becomes maximal, which isobserved as light leakage.

In conventional ECB type liquid crystal displays or TN type liquidcrystal displays, an absorption axis of a polarizing plate intersects ahorizontal direction of a screen, that is, a long side direction of anend portion of the polarizing plate, by 45°. Since a contractiondirection of the polarizing plate is in parallel to the long and shortside directions of the end portion of the polarizing plate, lightleakage becomes maximal in this arrangement. Accordingly, by making theabsorption axis of the polarizing plate in parallel or perpendicular tothe horizontal direction of the screen, that is, the long side directionof the end portion of the polarizing plate, it has been found that lightleakage can be suppressed in, particularly, ECB type liquid crystaldisplays or TN type liquid crystal displays. An example of such ECB typeliquid crystal displays will be described later with reference to FIG.2.

A TN type liquid crystal display employs a TFT driving method to displaya high quality image having high contrast with high precision. For theTFT driving, gate wiring lines and signal (or source) wiring lines arearranged in horizontal and vertical directions of a screen. Since acontraction direction of a polarizing plate is in parallel orperpendicular to these wiring lines, even if an absorption axis of thepolarizing plate is arranged in parallel or perpendicular to thesewiring lines, the absorption axis is arranged in substantial parallel orperpendicular to the maximal contraction direction of the polarizingplate, that is, long and short side directions of an end portion of thepolarizing plate, thereby suppressing light leakage. An example of suchTN type liquid crystal displays will be described later with referenceto FIG. 3.

On the other hand, in the above conventional liquid crystal displays,with the configuration that the absorption axis of the polarizing plateis in parallel or perpendicular to the horizontal direction of thescreen, there is a case where bilateral symmetry of color change isdeteriorated when the screen is viewed in an angle range of more thancontrast of 10° from the front of the screen or in a direction inclinedfrom the front of the screen. However, in the liquid crystal display ofthe invention that includes a light diffusion layer having a particularcharacteristic, it is confirmed that the bilateral symmetry is improved.

In addition, the configuration of the liquid crystal display of theinvention can be applied to an TPS type liquid crystal display. When theconfiguration of the liquid crystal display of the invention is appliedto the IPS type liquid crystal display, it has been found that coloringof light leaked out in the inclined direction when the black image isdisplayed in the conventional IPS type liquid crystal display isaveraged, thereby tuning into anchromatic color. An example of such anIPS type liquid crystal display will be described later with referenceto FIG. 4.

(Embodiments of Liquid Crystal Display of the Invention)

Hereinafter, exemplary embodiments of the liquid crystal display of theinvention will be described with reference to the accompanying drawings.

(ECB Type Liquid Crystal Display)

FIG. 1 is a schematic view showing an example of a liquid crystaldisplay, particularly, an ECB type liquid crystal display according toan exemplary embodiment of the invention.

Referring to FIG. 1, a liquid crystal display includes a liquid crystalcell 5 to 7 and a pair of polarizing plates 1 and 2 arranged at bothsides of the liquid crystal cell 5 to 7. Each of the polarizing plates 1and 2 includes a polarizer and a pair of protective films. Lightdiffusion layers (not shown) are disposed at an outer side of apolarizer 12 of an upper protective film 11 of an upper polarizing plate1 and an outer side of a polarizer 22 of a lower protective film 21 of alower polarizing plate 2, respectively. The protective films 11 and 21are also used as supports of the light diffusion layers. In addition, anupper optical compensation film 14 and a lower optical compensation film24, each having an optical compensation function, are arranged betweenthe liquid crystal cell and the pair of polarizing plates, respectively.The lower protective film 13 of the upper polarizing plate 1 may be alsoused as the support of the upper optical compensation film 14. The upperpolarizing plate is a stacked structure including the light diffusionlayer, the members 11 to 13, and, preferably, the member 14, and isassembled into the liquid crystal display. On the other hand, the upperprotective film 23 of the lower polarizing plate 2 may be also used asthe support of the lower optical compensation film 24. The lowerpolarizing plate is a stacked structure including the light diffusionlayer, the members 21 to 23, and, preferably, the member 24, and isassembled into the liquid crystal display.

In addition, in the invention, at least one of the polarizing plates 1and 2 may be a stacked structure including the light diffusion layer,the polarizer, and, preferably, the optical compensation film (forexample, the upper polarizing plate may be the stacked structureincluding the light diffusion layer, the members 11 to 13, and,preferably, the member 14), and both of the polarizing plates 1 and 2need not have the above stacked structure as shown in FIG. 1. That is,the liquid crystal display has only to a stacked structure including thelight diffusion layer, the polarizer, and, preferably, the opticalcompensation film. Accordingly, the configuration shown in FIG. 1 has nolimitation.

In the liquid crystal display of the invention, since the support of thelight diffusion layer may be also used as the protective film of one ofthe polarizers, and preferably, the transparent support of the opticalcompensation film may be also used as the protective film of the otherof the polarizers, a polarizing plate having the stacked structureincluding the light diffusion layer, the protective film (also used asthe support), the polarizer, the protective film (preferably also usedas the transparent support), and preferably, the optical compensationfilm in order may be used. This polarizing plate has not only apolarization function but also an effect of widening a viewing angle,particularly a contrast viewing angle, making change of a color viewingangle small, decreasing gray scale inversion and reducing display spots.In addition, this polarizing plate includes, preferably, the opticalcompensation film having the optical compensation function to opticallycompensate the liquid crystal display precisely with a simpleconfiguration. In the liquid crystal display, it is preferable that thelight diffusion layer, the protective film, the polarizer, thetransparent support, and preferably, the optical compensation film arestacked in order from the outer side of the device (from a side far awayfrom the liquid crystal cells).

Absorption axes 12D and 22D of the polarizers 12 and 22, alignmentdirections of the optical compensation films 14 and 24, and an alignmentdirection of liquid crystal molecules 6 can be adjusted to have anoptimal range depending on material used for the above members, adisplay mode, a stacked structure of the members, etc. In order toobtain high contrast, the absorption axes 12D and 22D of the polarizers12 and 22 are arranged to be substantially perpendicular to each other.However, the liquid crystal display of the invention is not limited tothis configuration.

Next, the configuration and operation of the liquid crystal displayshown in FIG. 1 will be described in more detail.

A rubbing direction 5RD of an upper substrate 5 and a rubbing direction7RD of a lower substrate 7 of the liquid crystal cell 5 to 7 are set tobe in parallel to each other, and the liquid crystal layer is in aparallel alignment without having a twisted structure. The uppersubstrate 5 and the lower substrate 7 have an alignment film (not shown)and an electrode layer (not shown), respectively. The alignment film hasa function of aligning the liquid crystal molecules 6. The electrodelayer has a function of applying a voltage to the liquid crystalmolecules 6. For example, transparent indium-tin-oxide (ITO) may be usedfor the electrode layer. In a mode of parallel alignment, liquidcrystals of Δn=0.0854 (589 nm, 20° C.) and Δ∈=+8.5 (for example,“MLC-9100” available from Merck, Co., Ltd.) may be provided between theupper and lower substrates.

Here, the brightness of white image display is varied depending on theproduct (Δn·d) of thickness d and anisotropic refractive index Δn. Inorder to obtain the maximal brightness, it is preferable that theproduct (Δn·d) is set to fall within a range of 0.2 to 0.4 μm. At leastone polarizer absorption axis interests the liquid crystal cellalignment direction (rubbing direction RD) adjacent to the axis by about45°, and an intersection angle between the upper and lower polarizerabsorption axes 12D and 22D is about 90°, which represents a crossNicol.

In a non-driving state where a driving voltage is not applied totransparent electrodes (not shown) of the liquid crystal cell substrates5 and 7, the liquid crystal molecules 6 in the liquid crystal layer arealigned in substantial parallel to planes of the substrates 5 and 7,and, as a result, light having polarization changed by a birefringenceeffect of the liquid crystal molecules 6 passes through the polarizer12. At this time, the product (Δn·d) of the liquid crystal layer is setsuch that transmitting light has maximal intensity. On the other hand,in a driving state where a driving voltage is applied to the transparentelectrodes (not shown), the liquid crystal molecules 6 tend to bealigned perpendicularly to the planes of the substrates 5 and 7depending on the magnitude of the applied voltage. However, since theliquid crystal molecules 6 are aligned in an inclined direction withrespect to the substrate planes near borders of the substrates althoughthe liquid crystal molecules 6 are aligned substantially perpendicularlyto the substrate planes near centers in a thickness direction of theliquid crystal layer between the substrates, the liquid crystalmolecules 6 are continuously obliquely aligned toward the centers in thethickness direction of the liquid crystal layer. Under such a state, itis difficult to obtain a full black image display. Simultaneously,average alignment of the liquid crystal molecules inclined near theborders of the substrates is changed depending on an observation angleand has a viewing angle dependency that transmittance and brightness arevaried depending on a viewing angle.

In order to overcome this problem, it is preferable that an opticalcompensation film to compensate a remaining phase difference of theliquid crystal layer near the borders of the substrates is firstdisposed, thereby obtaining a full black image display and henceimproving a front contrast ratio. In addition, as described in the abovePatent Document 1, it is preferable that an optical film to compensatethe continuously obliquely aligned liquid crystal layer is disposed,thereby improving a viewing angle characteristic. In addition, since theliquid crystal molecules 6 are inclined in a halftone display, thereoccurs a difference in luminance or color tone due to a difference inbirefringence between the liquid crystal molecules 6 when viewed fromthe inclination in the inclined direction and an opposite direction.When the liquid crystal display employs a multi domain structure inwhich one pixel of the liquid crystal display is divided into aplurality of regions, the viewing angle characteristic of luminance orcolor tone is averaged and hence improved.

Specifically, by dividing one pixel into two or more (preferably, 4 or8) regions having different initial alignment states of the liquidcrystal molecules and averaging these regions, luminance and color tunedepending on the viewing angle can be suppressed from being biased. Inaddition, the same effect is obtained even when one pixel is dividedinto two or more different regions where the alignment direction of theliquid crystal molecules is continuously changed under application of avoltage.

As described above, according to one of preferred aspects of theinvention, the invention provides a liquid crystal display in which anabsorption axis of a polarizer is in parallel or perpendicular to ahorizontal direction of a screen of the liquid crystal display. FIG. 2shows that the absorption axis of the polarizer is in parallel orperpendicular to the horizontal direction of the screen in the ECB typeliquid crystal display.

In addition, in the aspect shown in FIG. 2, the alignment controldirection of the optical compensation film including a discoticstructural unit intersects the absorption axis of the polarizer by,preferably, a range of 40 to 50°, more preferably 45°. In addition, thealignment control direction of the optical compensation film includingthe discotic structural unit intersects the alignment treatmentdirection of the liquid crystal layer by, preferably, a range of −20 to20°.

(TN Type Liquid Crystal Display)

Next, an exemplary embodiment where the invention is applied to a TNtype liquid crystal display will be described in detail with referenceto FIG. 3. FIG. 3 also shows that an absorption axis of a polarizer isin parallel or perpendicular to a horizontal direction of a screen inthe TN type liquid crystal display. Here, using nematic liquid crystalshaving positive dielectric anisotropy as field effect liquid crystals, aTFT (active) driving will be described by way of an example.

A liquid crystal cell 5 to 7 comprises an upper substrate 5, a lowersubstrate 7, and a liquid crystal layer having liquid crystal molecules6 interposed between these substrates 5 and 7. Alignment films (notshown) are formed on surfaces of the substrates 5 and 7 contacting theliquid crystal molecules 6 (hereinafter, these surfaces are sometimesreferred to as “inner surfaces”), and alignment of the liquid crystalmolecules 6 under application of no voltage or application of a lowvoltage is controlled by a rubbing treatment to which the alignmentfilms are subjected. In addition, transparent electrodes (not shown)that apply a voltage to the liquid crystal layer having the liquidcrystal molecules 6 are formed on the inner surfaces of the substrates 5and 7.

In the TN type liquid crystal display, under a non-driving state where adriving voltage is not applied to the electrodes, the liquid crystalmolecules 6 in the liquid crystal cell are aligned in substantialparallel to substrate planes and alignment direction is twisted by 90°between the upper and lower substrates. In case of a transmission typedisplay device, light emitted from a backlight unit has linearpolarization after passing through a lower polarizing plate 2. Thelinearly polarized light propagates along the twisted structure of theliquid crystal layer, rotates a polarizing plane by 90°, and then passesthrough the upper polarizing plate 1. Accordingly, the display devicedisplays a white image.

On the other hand, when an application voltage is increased, the liquidcrystal molecules 6 get stand perpendicularly to the substrate planeswhile being untwisted. In the TN type liquid crystal display underapplication of an ideal high voltage, the liquid crystal molecules 6 arenearly completely untwisted, and, accordingly, have a state of alignmentnearly perpendicular to the substrate planes. At this time, since thereis no twisted structure in the liquid crystal layer, the linearlypolarized light that passed through the lower polarizing plate 2propagates without rotating the polarizing plane and is perpendicularlyincident into an absorption axis of the upper polarizing plate 1.Accordingly, the light is shielded and the display device displays ablack image.

In this manner, the TN type liquid crystal display achieves a functionas a display device by shielding or transmitting the polarized light. Ingeneral, a contrast ratio as a numerical value to indicate displayquality is defined by a ratio of white display luminance to blackdisplay luminance. A higher contrast ratio gives a higher qualitydisplay device. In order to increase a contrast ratio, it is importantto maintain a polarization state in a liquid crystal display.

Hereinafter, an example of a configuration of the TN mode liquid crystalcell is described. A liquid crystal cell is manufactured by rubbing andaligning the liquid crystals having positive dielectric anisotropy,anisotropic refractive index, Δn=0.0854 (589 nm, 20° C.) and Δ∈=+8.5,and is disposed between the upper and lower substrates 5 and 7. Thealignment of the liquid crystal layer is controlled by the alignmentfilm and the rubbing treatment. A director, a so-called tilt angle,indicating the alignment direction of the liquid crystal molecules isset to falls within a range of, preferably, about 0.1° to 10°. In thisembodiment, the director is set to be 3°. The rubbing treatment isperformed in a direction perpendicular to the upper and lowersubstrates, and the size of the tilt angle can be controlled by rubbingstrength and number. The alignment films are formed by applying andfiring a polyimide film. The size of a twist angle of the liquid crystallayer is defined by an intersection angle in a rubbing direction betweenthe upper and lower substrates and a chiral agent added to liquidcrystal material. In this embodiment, a chiral agent having a pitch of60 μm or so is added so that the twist angle is about 90°. The thicknessd of the liquid crystal layer is set to be 5 μm.

In addition, liquid crystal material LC is not particularly limited aslong as it is nematic liquid crystal. As dielectric anisotropy Δ∈increases, the driving voltage can be further reduced. As refractiveindex anisotropy Δn decreases, the thickness (gap) of the liquid crystallayer can be further thickened, thereby shortening time taken to injectand seal liquid crystals and reducing unbalance of the gap. In addition,as Δn increases, a cell gap can be further decreased, thereby allowing ahigher speed response. In general, Δn is set to fall within a range of0.04 to 0.28, the cell gap is set to fall within a range of 1 to 10 μm,and the product of Δn and d is set to fall within a range of 0.25 to0.55 μm.

The absorption axis 12D of the upper polarizer 12 and the absorptionaxis 22D of the lower polarizer 22 are stacked substantiallyperpendicularly to each other, the absorption axis 12D of the upperpolarizer 12 and the rubbing direction (alignment axis) 5RD of the uppersubstrate 5 of the liquid crystal cell are stacked in substantialparallel to each other, and the absorption axis 22D of the lowerpolarizer 22 and the rubbing direction (alignment axis) 7RD of the lowersubstrate 7 of the liquid crystal cell are stacked in substantialparallel to each other. Although the transparent electrodes (not shown)are formed at the inner sides of the alignment films of the upper andlower substrates 5 and 7, the liquid crystal molecules 6 in the liquidcrystal cell are aligned in substantial parallel to the substrate planesunder a non-driving state where the driving voltage is not applied tothe electrodes, and as a result, the polarized light that passes throughthe liquid crystal panel propagates along the twist structure of theliquid crystal molecules 6 and rotates the polarizing plane by 90°. Thatis, the liquid crystal display realizes the white image display underthe non-driving state. On the other hand, the liquid crystal molecules 6are aligned in a direction inclined by an angle with respect to thesubstrate planes under a driving state, and the light that passedthrough the lower polarizing plate 2 has no retardation in the liquidcrystal layer by the optical compensation layers 14 and 24, passesthrough the liquid crystal layer 6 with its polarization stateunchanged, and then is shielded by the polarizer 12. In other words, theliquid crystal display realizes the ideal black image display under thedriving state.

A light diffusion layer (not shown) is disposed in the outside of thepolarizer 12 of an upper (viewing side) protective film 11 of the upperpolarizing plate 1 or in the outside of the polarizer 22 of a lowerprotective film 21 of the lower polarizing plate 2. The protective films11 and 21 are also used as supports of the light diffusion layer. Inaddition, protective films 23 and 13 near the liquid crystal cell of theupper and lower polarizing plates may be also used as supports ofoptically anisotropic layers 14 and 24, and the upper and lowerpolarizing plates 1 and 2 may be integrally stacked with opticallyanisotropic layers 14 and 24, and the stacked structure thereof may beassembled into the liquid crystal display.

In the liquid crystal display of the invention, the support of the lightdiffusion layer may be also used as a protective film of one of thepolarizers. Preferably, a transparent support of an optical compensationsheet may be also used as a protective film of the other of thepolarizers. That is, an integrated elliptical polarizing plate includingthe light diffusion layer, the transparent protective film (also used asthe support), the polarizer, the transparent protective film (preferablyalso used as the transparent support), and preferably, the opticallyanisotropic layer in order may be used. This integrated ellipticalpolarizing plate has an effect of widening a contrast viewing angle,making change of a color viewing angle small, decreasing gray scaleinversion and reducing display spots. In addition, it is preferable thatthis integrated elliptical polarizing plate has the opticallyanisotropic layer having an optical compensation function. When theintegrated elliptical polarizing plate is used, it is possible tocompensate the liquid crystal display precisely with a simpleconfiguration. In the liquid crystal display, it is preferable that thelight diffusion layer, the transparent protective film, the polarizer,the transparent support, and preferably, the optically anisotropic layerare stacked in order from the outside of the device (side far away fromthe liquid crystal cell).

In addition, when the liquid crystal display employs a multi domainstructure in which one pixel is divided into a plurality of regions,vertical and horizontal viewing angle characteristics are averaged,thereby improving display quality.

(IPS Type Liquid Crystal Display)

Next, an embodiment where the invention is applied to an IPS type liquidcrystal display will be described in detail with reference to FIG. 4.

A liquid crystal display shown in FIG. 4 includes a liquid crystal cell5 to 7, and upper and lower polarizing plates 1 and 2 with the liquidcrystal cell interposed therebetween. The liquid crystal cell 5 to 7comprises a liquid crystal cell upper substrate 5, a liquid crystal celllower substrate 7, and a liquid crystal layer 6 interposed therebetween.Alignment direction of the liquid crystal layer 6 is controlled bydirections 5RD and 7RD of rubbing treatment to which opposite planes ofthe substrates 5 and 7 are subjected.

The upper polarizing plate comprises a pair of transparent protectivefilms 11 and 13 and a polarizer 12 interposed therebetween (thetransparent protective film 13 being disposed at a side closer to theliquid crystal cell). It is preferable that an absorption axis 12D ofthe polarizer 12 is in substantial parallel to roll moving directions(MD directions) 11D and 13D of the transparent protective films 11 and13. When the absorption axis 12D of the polarizer 12 is in substantialparallel to MD directions 11D and 13D, effects of improvement ofmechanical stability and uniformity of optical performance can beobtained. In addition, when the absorption axis 12D of the polarizer 12is in substantial parallel to the MD direction 11D disposed at a sidefar away from the liquid crystal cell, mechanical reliability such asprevention of dimension change or curl of the polarizing plate isimproved. The same effect is obtained even when the absorption axis 12Dis perpendicular to the MD direction 13D. In addition, if the thicknessor strength of the transparent protective films 11 and 13 is sufficient,the same effect is obtained even when the absorption axis 12D intersectsthe MD directions 11D and 13D of the protective films by differentangles.

It is preferable that the lower polarizing plate has the sameconfiguration as the upper polarizing plate as shown in FIG. 4. Inaddition, it is preferable that a polarizer 22 is in substantialparallel or perpendicular to an MD direction 23D of a protective film 23at a side closer to the liquid crystal cell of the polarizer 22. Whenthe MD directions 23D and 21D of the transparent protective films 23 and21 are perpendicular to each other, birefringences of the protectivefilms are cancelled each other, thereby reducing deterioration ofoptical characteristics of light perpendicularly incident into theliquid crystal display. In addition, when the MD directions 23D and 21Dare in parallel to each other, retardation which may remain in theliquid crystal layer may be compensated by the birefringences of theprotective films.

FIG. 5 is a schematic side sectional view showing an IPS mode liquidcrystal cell. FIG. 5 shows a portion of one pixel of the IPS mode liquidcrystal cell although the cell typically has a plurality of pixels byelectrodes in the form of a matrix. Linear electrodes 91 are formed atinner sides of a pair of transparent substrates 5 and 7, and analignment control film (not shown) is formed on the electrodes 91.Bar-like liquid crystal molecules 6 interposed between the substrates 5and 7 are aligned to form a slight angle with respect to a longitudinaldirection of the linear electrodes 91 under application of no voltage.In addition, in this case, dielectric anisotropy is assumed to bepositive. When an electric field 9D is applied, the direction of theliquid crystal molecules 6 is changed in an electric applicationdirection. It is possible to change light transmittance by arranging thepolarizing plates 1 and 2 at a predetermined angle. In addition, anangle between the surface of the substrate 7 and the electric fieldapplication direction 9D is less than, preferably, 20°, more preferably,10°. That is, it is preferable that the surface of the substrate 7 is insubstantial parallel to the electric field application direction 9D.Hereinafter, in the invention, an electric field forming an angle ofless than 20° with the surface of the substrate 7 is generally referredto as a parallel electric field. In addition, the same effect isobtained irrespective of whether the electrodes 91 are formed on both orone of the upper and lower substrates.

In this manner, the IPS mode liquid crystal cell is aligned in parallelto the substrate surface under application of no voltage or underapplication of a low voltage. The alignment is generally controlled byapplying and rubbing the alignment film. However, alignment spots areapt to occur in this alignment treatment. As described above, since theIPS mode liquid crystal cell is aligned in parallel to the substratesurface, this alignment spots cause a big retardation, particularlyleading to unbalanced luminance spots of light leakage in the blackimage display. On the other hand, in VA, TN and OCB modes, since theliquid crystal molecules are aligned perpendicularly to the substratesurface in the black image display, the luminance spots are small sincethe retardation is small although the alignment spots are large.

FIG. 6 is a schematic sectional view showing an IPS mode liquid crystalcell with higher speed response and higher transmittance. Unlike FIG. 5,FIG. 6 shows a double-layered structure in which an insulating layer 93is interposed between two electrodes. A lower electrode may be anelectrode not patterned or a linear electrode. An upper electrode ispreferably a linear electrode, but may have any shape such as a netknot-like shape, a spiral shape, a dot shape and the like as long as ithas a shape to allow an electric field from the lower electrode 92 topass. In addition, a floating electrode having a neutral potential maybe added. In addition, the insulating layer 93 may be made of any ofinorganic material such as SiO or nitride oxide and organic materialsuch as acryl or epoxy.

In the IPS mode, since a contrast ratio is increased by hightransmittance, luminance spots due to in-plane alignment spots in theblack image display are apt to be observed. In addition, since theintensity of electric field is high, luminance spots are also apt tooccur under application of a low voltage.

Nematic liquid crystal having positive dielectric anisotropy Δ∈ is usedas liquid crystal material LC. The thickness (gap) of the liquid crystallayer is more than 2.8 μm and less than 4.5 μm. In this manner, when theretardation (Δn·d) is more than 0.25 μm and less than 0.32 μm, since thetransmittance has little wavelength dependency in a range of visiblelight wavelength, a transmittance characteristic can be more easilyobtained. By combination of the alignment film and the polarizing plate,which will be described later, the maximal transmittance can be obtainedwhen the liquid crystal molecules are rotated by 45° in the electricfield application direction from the rubbing direction. In addition, thethickness (gap) of the liquid crystal layer is controlled by polymerbeads. Of course, the same gap can be obtained in glass beads, glassfiber, and a pillar-like spacer made of resin. In addition, the liquidcrystal material LC is not particularly limited as long as it is nematicliquid crystal. As dielectric anisotropy Δ∈ increases, the drivingvoltage can be further reduced. As refractive index anisotropy Δndecreases, the thickness (gap) of the liquid crystal layer can befurther thickened, thereby shortening time taken to inject and sealliquid crystals and reducing unbalance of the gap.

Also in the IPS mode, the polarizing plate of the invention may beapplied to the liquid crystal display of the invention. As describedabove, the support of the light diffusion layer may be also used as aprotective film of one of the polarizers. Preferably, since atransparent support of an optical compensation film may be also used asa protective film of the other of the polarizer, an integratedelliptical polarizing plate including the light diffusion layer, theprotective film (also used as the support), the polarizer, theprotective film (preferably also used as the transparent support), andpreferably, the optical compensation film in order may be used. Thisintegrated elliptical polarizing plate has not only the polarizingfunction but also an effect of widening a viewing angle, particularly acontrast viewing angle, making change of a color viewing angle small,decreasing gray scale inversion and reducing display spots. In addition,it is preferable that this integrated elliptical polarizing plate hasthe optical compensation film having an optical compensation function.When the integrated elliptical polarizing plate is used, it is possibleto compensate the liquid crystal display precisely with a simpleconfiguration. In the liquid crystal display, it is preferable that thelight diffusion layer, the protective film, the polarizer, thetransparent support, and preferably, the optical compensation film arestacked in order from the outside of the device (side far away from theliquid crystal cell).

The liquid crystal display used in the invention is effective for an OCBmode, a VA mode, a HAN mode, and a STN mode in addition to theabove-described display mode.

The liquid crystal display of the invention is not limited to theabove-described configuration, but may include other members. Forexample, a color filter may be interposed between the liquid crystalcell and the polarizer. In addition, a separate optical compensationfilm may be interposed between the liquid crystal cell and thepolarizing plate. In addition, in case of a transmission type liquidcrystal display, a backlight unit having a light source such as a coldcathode or hot cathode fluorescent tube, a light emitting diode, a fieldemission device, or an electroluminescence device may be disposed behindthe liquid crystal cell. In addition, the liquid crystal display of theinvention may be of a reflection type. In this case, only one polarizingplate may be disposed at an observation side, and a reflecting film isdisposed behind the liquid crystal cell or at an inner side of the lowersubstrate of the liquid crystal cell. Of course, a front light unitusing the light source may be provided at a liquid crystal cellobservation side.

The liquid crystal display of the invention includes image direct-viewtype, image projection type and light modulation type display devices.The invention is particularly effective for an active matrix liquidcrystal display using three or two terminal semiconductor devices suchas TFT or MIM. Of course, the invention is also effective for a passivematrix liquid crystal display represented by a STN type which is calleda time division driving.

The liquid crystal display of the invention has an effect of widening acontrast viewing angle, making change of a color viewing angle small,decreasing gray scale inversion, and reducing display spots such asluminance spots and color spots by the polarizing plate having aparticular light diffusion layer. Further, by setting a particularrelationship between the retardation axis of the protective film of thepolarizing plate and the absorption axis of the polarizing plate, theviewing angle of the liquid crystal display can be improved.Furthermore, when the optical compensation film is interposed betweenthe polarizing plate and the liquid crystal cell, the viewing angle canbe further improved.

According to another aspect, the invention provides a liquid crystaldisplay comprising a pair of substrates disposed opposite to each other,at least one of which has an electrode, a liquid crystal layercontaining liquid crystal molecules controlled to be aligned by analignment axis of each of opposite planes of the pair of substrates, anda pair of polarizing plates that is formed by stacking an adhesivelayer, an optical compensation sheet, a polarizer, and a protectivelayer in order, with the liquid crystal layer interposed therebetween,wherein an absorption axis direction of the polarizing plates forms anangle of more than 5° and less than 40° with a horizontal direction or avertical direction of a screen of the display device (hereinafter, thisaspect is sometimes referred to as a preferred aspect (II)).

The present inventors have found that, when a liquid crystal panel isheated (that is, when it is put into and then drawn out of a dryer ofhigh temperature as a condition where light leakage due to thermaldistortion is remarkably observed), the light leakage due to the thermaldistortion occurring in a circumference or corner of the liquid crystalpanel is decreased in a liquid crystal display using a polarizing platepunched with an angle at which an absorption axis direction of thepolarizing plate is deviated from 45°, that is, an intersection angle of40° or less between the absorption axis direction of the polarizingplate and an end line of the polarizing plate, as compared to a liquidcrystal display using a polarizing plate punched to form an angle of 45°between an end line of a polarizing plate and an absorption axisdirection of the polarizing plate, as in a conventional TN mode liquidcrystal display.

The reason for this decrease of the light leakage is that most of aretardation axis of a phase difference occurring in portions of anoptical compensation sheet due to the thermal distortion is insubstantial parallel or perpendicular to the end line of the polarizingplate, and, when the polarizing plate punched to form an angle of 45°between the end line of the polarizing plate and the absorption axisdirection of the polarizing plate is used, an intersection angle betweenthe retardation axis of the phase difference occurring in portions ofthe optical compensation sheet due to the thermal distortion and theabsorption axis direction of the polarizing plate becomes 45°, andaccordingly, the light leakage becomes maximal.

On the other hand, when the polarizing plate punched with the angle atwhich the absorption axis direction of the polarizing plate is deviatedfrom 45° with respect to the end line of the polarizing plate, theintersection angle between the retardation axis of the phase differenceoccurring in portions of the optical compensation sheet due to thethermal distortion and the absorption axis direction of the polarizingplate is deviated from 45°, and accordingly, the light leakage doe notbecome maximal. Accordingly, it has been found that light leaked out dueto the phase difference occurring in the portions of the opticalcompensation sheet is decreased.

Further, the present inventors has been found that it is preferable toform an angle of more than 5° between the absorption axis direction ofthe polarizing plate and sides of the polarizing plate from a standpointof improvement of bilateral symmetry of image brightness, color or thelike, which is provided as the preferred aspect (II).

When the invention is used in a TN mode transmission type liquid crystaldisplay, like a TN mode transmission type liquid crystal display usedtypically, an absorption axis direction TN2 of a polarizing plate at anobserver side and an absorption axis direction TN13 of a polarizingplate at a backlight side are stacked to be perpendicular to each other(cross Nicol arrangement), the absorption axis direction TN2 of thepolarizing plate at the observer side and a rubbing direction (alignmentcontrol direction) TN6 of an electrode substrate at the observer side ofa liquid crystal cell are stacked to be in parallel to each other, andthe absorption axis direction TN13 of the polarizing plate at thebacklight side and a rubbing direction (alignment control direction) TN9of a substrate at the backlight side of the liquid crystal cell arestacked to be in parallel to each other (FIG. 7). In the TN modetransmission type liquid crystal display, unlike the typical TN modetransmission type liquid crystal display where the absorption axisdirection of the polarizing plate or the rubbing direction of the liquidcrystal cell has an inclined angle of 45° (FIG. 8B), since anintersection angle between the absorption axis direction TN2 and TN13 ofthe polarizing plate and the end line of the polarizing plate isdeviated from 45° (FIG. 8A), an intersection angle between the rubbingdirection TN6 and TN9 of the liquid crystal cell and the end line of thepolarizing plate or the liquid crystal cell is also deviated from 45°.

In addition, the polarizing plate of the invention may be alsoadvantageously used in liquid crystal displays employing an OCB(Optically Compensatory Bend) mode, a VA (Vertically Aligned) mode, anIPS (In-Plane Switching) mode, etc., in addition to the TN mode and ECBmode liquid crystal cells.

That is, the liquid crystal display of the invention can be applied toTN, ECB, OCB, VA, IPS modes and the like.

According to still another aspect (III-1), the invention provides aliquid crystal display comprising: a pair of first and second oppositesubstrates, at least one of which has a transparent electrode; a liquidcrystal layer interposed between the pair of first and second oppositesubstrates, wherein liquid crystal molecules are aligned in substantialparallel to surfaces of the first and second opposite substrates underapplication of no voltage and a twist angle between the first and secondopposite substrates is 45° or less; a plurality of pixels including aplurality of electrodes that applies a voltage to the liquid crystallayer, wherein the liquid crystal display displays an image in anormally white mode, wherein each of the plurality of pixels has a firstsub pixel and a second sub pixel that apply different voltages to theliquid crystal layer, and wherein the liquid crystal display is adaptedto represent 0 to n gray scales (n being an integer number of 1 or more,higher n representing a gray scale having higher luminance), andeffective voltages V1(k) and V2(k) applied to the liquid crystal layerof the first and second sub pixels satisfy the following relationshipwhen the liquid crystal display represents at least k gray scale(0<k≦n−1).|V1(k)−V2(k)|>0(Volt)

According to still another aspect (III-2), the invention provides aliquid crystal display comprising: a liquid crystal layer interposedbetween a pair of first and second opposite substrates, at least one ofwhich has a transparent electrode, wherein liquid crystal molecules arealigned in substantial parallel to surfaces of the first and secondopposite substrates under application of no voltage and a twist anglebetween the first and second opposite substrates is about 90°; and aplurality of pixels including a plurality of electrodes that applies avoltage to the liquid crystal layer, wherein the liquid crystal displaydisplays an image in a normally white mode, wherein each of theplurality of pixels has a first sub pixel and a second sub pixel thatapply different voltages to the liquid crystal layer, and wherein theliquid crystal display is adapted to represent 0 to n gray scales (nbeing an integer number of 1 or more, higher n representing a gray scalehaving higher luminance), and effective voltages V1(k) and V2(k) appliedto the liquid crystal layer of the first and second sub pixels satisfythe following relationship when the liquid crystal display represents atleast k gray scale (0<k≦n−1).|V1(k)−V2(k)|>0(Volt)

According to the above aspects, a liquid crystal display of a normallywhite mode having a good viewing angle characteristic and a reducedviewing angle dependency of γ characteristic can be provided. Inaddition, according to one aspect of the invention, a liquid crystaldisplay of a normally white mode having a reduced viewing angledependency of γ characteristic, a reduced light leakage in an inclineddirection in black image display, a good viewing angle characteristic,and a good viewing contrast can be provided.

Now, a configuration of a liquid crystal display according to anembodiment of the invention will be described with reference to FIG. 10.In FIG. 10, an upper side indicates a display plane of the device and alower side indicates a rear side of the device.

FIG. 10 is a schematic view showing an embodiment in which the inventionis applied to an ECB type liquid crystal display. A liquid crystaldisplay 100 shown in FIG. 10 comprises an ECB mode liquid crystal cell309 to 313, a pair of polarizing plates arranged at both sides of theliquid crystal cell, an upper polarizing plate 301 to 306, and a lowerpolarizing plate 316 to 321. An upper optical compensation film 307 anda lower optical compensation film 314 are interposed between the upperpolarizing plate and the liquid crystal call and between the lowerpolarizing plate and the liquid crystal cell, respectively.

The upper polarizing plate comprises an upper polarizer 303 and a pairof protective films 301 and 305 with the upper polarizer 303therebetween, and the lower polarizing plate comprises a lower polarizer318 and a pair of protective films 316 and 320 with the lower polarizer318 therebetween. An upper optical compensation film 307 and a loweroptical compensation film 314 may be integrally stacked with the upperpolarizing plate and the lower polarizing plate, respectively, and thestacked structure thereof may be assembled into the liquid crystaldisplay. For example, if the optical compensation films 307 and 314 arean optically anisotropic layer formed of a liquid crystal composition,the lower protective film 305 of the upper polarizing plate may be alsoused as a support of the optically anisotropic layer as the upperoptical compensation film 307, and the upper protective film 316 of thelower polarizing plate may be also used as a support of the opticallyanisotropic layer as the lower optical compensation film 314.

An alignment film (not shown) and an electrode layer (not shown) areformed at inner sides of an upper substrate 309 and a lower substrate312 of the liquid crystal cell 309 to 313, respectively. An innersurface of the alignment film is beforehand subjected to a rubbingtreatment, and alignment control directions 310 and 313 are defined by arubbing axis. The alignment control directions (for example, rubbingdirections) 310 and 313 of the upper substrate 309 and the lowersubstrate 312 are set to be in parallel to each other and the liquidcrystal layer is aligned in parallel without having a twist structure.The alignment film has a function to align liquid crystal molecules 311.In the parallel mode, nematic liquid crystal material having positivedielectric anisotropy Δ∈ is filled between the upper and lowersubstrates. Assuming that the thickness of the liquid crystal layer is dand refractive index anisotropy of the nematic liquid crystal materialis Δn, the product Δn·d has an effect on brightness in white imagedisplay. In order to obtain the maximal brightness, it is preferablethat the liquid crystal cell is designed such that the product Δn·dfalls within a range of 0.2 to 0.4 μm.

In the liquid crystal display 100 of this embodiment, the upperpolarizer 303 and the lower polarizer 318 are arranged such that anabsorption axis 304 of the upper polarizer 303 is perpendicular to anabsorption axis 319 of the lower polarizer 318 to thereby display animage in a normally white mode. Specifically, in a non-driving statewhere a driving voltage is not applied to transparent electrodes (notshown) of the liquid crystal cell substrates 309 and 312, the liquidcrystal molecules 311 in the liquid crystal layer are aligned insubstantial parallel to planes of the substrates 309 and 312 by lessthan 45°, and, as a result, light that passed through the lowerpolarizer 318 and has polarization changed by a birefringence effect ofthe liquid crystal molecules 311 passes through the polarizer 303. Atthis time, the product (Δn·d) of the liquid crystal layer is set suchthat transmitting light has maximal intensity to display a white image.On the other hand, in a driving state where a driving voltage is appliedto the transparent electrodes (not shown), the liquid crystal molecules311 are aligned perpendicularly to the surfaces of the substrates 309and 312 depending on the magnitude of the applied voltage, and thepolarized light that passed through the lower polarizer 318 is absorbedby the upper polarizer 303 to display an black image, with itspolarization state unchanged. By changing a voltage applied to theliquid crystal layer, birefringence of the liquid crystal molecules 311is controlled, the transmittance is changed, and gray scales 0 to n (nis an integer number of more than 1. A larger n indicates a gray scalehaving higher luminance) can be represented.

In the liquid crystal display 100 of this embodiment, the liquid crystalcell comprises a plurality of pixel including a plurality of electrodesthat applies a voltage to the liquid crystal layer. FIG. 11 shows anexemplary configuration of one pixel of the liquid crystal display 100.For reference, FIG. 12 shows an exemplary configuration of one pixel ofa conventional liquid crystal display 100′.

The liquid crystal display 100 of the invention comprises a plurality ofpixels 350 arranged in the form of a matrix. Each of the plurality ofpixel 350 comprises two pixel electrode 358 a and 358 b and a counterelectrode (not shown) as shown in FIG. 11. The counter electrode istypically constituted by one common electrode for all the pixels 350.Although the conventional liquid crystal display 100′ shown in FIG. 12includes only one pixel electrode 358′, the liquid crystal display 100of this embodiment includes two sub pixels 358 a and 358 b in one pixel350 so that different voltages can be applied to respective liquidcrystal layer.

For a conventional ECB mode liquid crystal display having the electrodestructure of the liquid crystal display 100′ shown in FIG. 12, whentransmittance for an application voltage is plotted, a curve indicatedby transmittance measured in front observation is not coincident with acurve indicated by transmittance measured in side observation. Suchdiscrepancy indicates that a γ characteristic of display in the frontobservation is different from a γ characteristic of display in the sideobservation. An ideal gray scale characteristic of a liquid crystaldisplay indicates that a gray scale in the side observation (value in avertical axis) is in direct proportion to a gray scale in the frontobservation (value in a horizontal axis), as shown in FIG. 13. On theother hand, a viewing angle gray scale characteristic in the sideobservation indicates a curve. Deviation from a straight line indicatinga front characteristic of the curve indicates a quantitative deviation(difference) of γ characteristics in respective viewing angles, that is,a quantitative deviation (difference) of gray scales in the frontobservation and respective viewing angle observations.

One of objects of the invention is to reduce this deviation in anormally white mode liquid crystal display. It is ideally preferablethat curves L3 and LU3 indicating gray scale characteristics at a right60° viewing angle and a right and upper 60° viewing angle is changed toa straight line coincident with a straight line indicating a front grayscale characteristic N3.

To achieve this object of the invention, in the liquid crystal display100 of this embodiment, each of the plurality of pixels 350 has a firstsub pixel 350 a and a second sub pixel 350 b that apply differentvoltage, as shown in FIG. 11. In addition, when each of the plurality ofpixels 350 displays an image with a gray scale of at least k (0<k≦n−1),effective voltages V1(k) and V2(k) respectively applied to liquidcrystal layers of the first and second sub pixels 350 a and 350 bsatisfy an equation of |V1(k)−V2(k)|>0. In this manner, when each pixelis divided into a plurality of sub pixels and different voltages areapplied to liquid crystal layers of the plurality of sub pixels, amixture of different γ characteristics is observed, thereby improving aviewing angle dependency of a halftone γ characteristic in a normallywhite mode.

In addition, by using an optically anisotropic layer formed of acomposition containing a disk-like liquid crystal compound, which willbe described later, as the upper and lower optical compensation films307 and 314, a liquid crystal display with reduced light leakage in aninclined direction in black image display and good viewing anglecontrast can be obtained. Here, it is important to make an effectivevoltage V1(0) substantially equal to an effective voltage V2(0) in theblack image display, that is, in a gray scale of 0. Then, the first subpixel and the second sub pixel have the same liquid crystal displaystate in the black image display, and light leakage is reduced in theblack image display when the optical compensation film 307 or 314 isarranged, thereby improving a contrast ratio.

In addition, for a difference ΔV(n)(=|V1(n)−V2(n)|) between effectivevoltages applied to the liquid crystal layers of the first and secondsub pixels 350 a and 350 b between gray scales, it is preferable but notnecessary that a difference ΔV(k) between effective voltages V1 and V2in k (0<k≦n−1) gray scale representation and a difference ΔV(k+1)between effective voltages V1 and V2 in k+1 gray scale representationsatisfy a relationship of ΔV(k+1)≦ΔV(k).

In order to apply the effective voltages satisfying the aboverelationship to the liquid crystal layers of the sub pixels 350 a and350 b, the liquid crystal display 100 of this embodiment has theconfiguration shown in FIG. 11. As described above, although theconventional liquid crystal display 100′ shown in FIG. 12 includes onlyone pixel electrode 358′ connected to a signal line 354′ via a TFTelectrode 356′ in one pixel 350′, the liquid crystal device 100 of thisembodiment includes two sub pixel electrode 358 a and 358 b connected todifferent signal lines 354 a and 354 b via TFT electrodes 356 a and 356b, respectively, in one pixel 350. The sub pixels 350 a and 350 bcompose one pixel 350, and gates of the TFT electrodes 356 a and 356 bare connected to a common scan line (gate bus line) 352 and are turnedon/off by the same scan signal. A signal voltage (gray scale voltage) isapplied to the signal lines (source bus line) 354 a and 354 b to satisfythe above relationship. In addition, it is preferable that the gates ofthe TFT electrodes 356 a and 356 b are in common use.

In the configuration shown in FIG. 11, it is preferable that an intervalof a center line in parallel to the common scan line 352 in each of thesub pixels 350 a and 350 b is equal to about ½ of an arrangement pitchof the scan line 352. In addition, it is preferable that an area of thesub pixel 350 a is equal to or smaller than an area of the sub pixel 350b.

In addition, if each of the plurality of pixels has 3 or more subpixels, it is preferable that an area of a sub pixel to which thehighest effective voltage is applied is not larger than areas of othersub pixels.

In addition, the configuration where the effective voltage satisfyingthe above relationship is applied to the liquid crystal layers of theplurality of sub pixels is not limited to the configuration shown inFIG. 11. For example, in a configuration where each of the first andsecond sub pixels has a storage capacitor including a storage capacitorelectrode electrically connected to a sub pixel electrode, an insulatinglayer, and a storage capacitor counter electrode facing the storagecapacitor electrode via the insulating layer, an effective voltageapplied to a liquid crystal layer of the first sub pixel may bedifferent from an effective voltage applied to a liquid crystal layer ofthe second sub pixel by constructing the storage capacitor counterelectrode in an electrically independent manner for each of the firstand second sub pixels and dividing capacitance of the storage capacitorby varying a voltage applied to the storage capacitor counter electrode(also being referred to as a storage capacitor counter voltage). Byadjusting the size of capacitance of the storage capacitor and themagnitude of the voltage applied to the storage capacitor counterelectrode, the magnitude of the effective voltage applied to the liquidcrystal layer of each sub pixel can be controlled.

With the above configuration, since different signal voltages need notbe applied to the sub pixel electrodes (358 a and 358 b in FIG. 11), theTFT electrode layers (356 a and 356 b in FIG. 11) may be connected tothe common signal line and the same signal voltage may be applied to theTFT electrode layers. Accordingly, the number of signal lines is thesame as in the conventional liquid crystal display 100′ shown in FIG. 12and a signal line driving circuit may have the same configuration as inthe conventional liquid crystal display 100′. Of course, since the TFTelectrode layers (356 a and 356 b in FIG. 11) are connected to the samescan line, it is preferable to employ a configuration using gates of theTFT electrode layers in common, as described above.

As described above, in the liquid crystal display 100 shown in FIG. 10,in a driving state where a driving voltage is applied to the transparentelectrodes (not shown), the liquid crystal molecules 311 are alignedperpendicularly to the surfaces of the substrates 309 and 312 to displayan black image depending on the magnitude of the applied voltage.However, although the liquid crystal molecules 311 are alignedsubstantially perpendicular to the substrate planes near centers in athickness direction between the substrates, the liquid crystal molecules311 are aligned in parallel to the substrate planes near borders of thesubstrates and are continuously obliquely aligned toward the centers inthe thickness direction. Under such a state, it is difficult to obtain afull black image display. In the liquid crystal display 100 of thisembodiment, in order to compensate a remaining phase difference of theliquid crystal layer, the optical compensation film 307 or 314 isdisposed to reduce light leakage in the black image display, therebyimproving a contrast ratio. It is preferable that the upper and loweroptical compensation films 307 and 314 are an optically anisotropiclayer formed of a liquid crystal composition containing a disk-likecompound. It is preferable that the disk-like compound is a liquidcrystal compound. For example, the optically anisotropic layer may beformed by controlling alignment of molecules of the disk-like compoundby respective alignment control directions (rubbing axis directions ifan alignment film having a rubbing treatment surface is used) 308 and315 and fixing the alignment state. It is particularly preferable thatan optically anisotropic layer formed by hybrid-aligning molecules ofthe disk-like compound and fixing the alignment state is used as theoptical compensation films 307 and 314. It is preferable that thealignment control directions 308 and 315 of the upper and lower opticalcompensation films 307 and 314 are 0 to 10° with respect to thealignment control directions (generally rubbing axis directions) 310 and313 of the liquid crystal molecules 311. In addition, the alignmentcontrol directions 308 and 315 of the upper and lower opticalcompensation films 307 and 314 intersect the absorption axis of thepolarizing plate arranged at a position closer than the films 307 and314 by, preferably, ±20 to 70°, more preferably, ±35 to 55°.

In addition, the configuration of the liquid crystal display of theinvention is not limited to the above described configuration. Forexample, the absorption axes 304 and 319 of the upper and lowerpolarizers 303 and 318, the alignment directions of the opticalcompensation films 307 and 314, and the alignment directions of theliquid crystal molecules 311 may be adjusted to fall within an optimalrange depending on material used for each member, a display mode, astacked structure of the members, etc. In order to a high contrast, itis preferable that the absorption axis 304 of the upper polarizer 303 isin substantially perpendicular to the absorption axis 319 of the upperpolarizer 318 and the absorption axes 304 and 319 intersect thealignment axes 310 and 313 of the liquid crystal molecules 311 by about45°, respectively. The alignment control directions 310 and 313 of theliquid crystal molecules 311 are alignment axes to control alignment ofthe liquid crystal molecules 311 having alignment films (not shown)formed at inner surfaces of the upper and lower substrates 309 and 312.For example, if the alignment films have rubbing treatment surfaces, thealignment films, the alignment control directions 310 and 313 arecoincident with rubbing axes.

When the protective films 305 and 316, which are arranged at the liquidcrystal cell, of the protective films of the polarizers have opticallyrefractive index anisotropy for visible light (a preferred range of Reand Rth of the protective films will be described later), and an opticalaxis of the optical compensation film (an average alignment direction ofa molecule long axis) is arranged in parallel to the substrate surfacein a direction in which a phase difference of the liquid crystal layeris removed, viewing angle performance in the black image display andhalftone image display is further improved, a range of high contrast isfurther widened, and a region of gray scale inversion is significantlyreduced.

It is preferable that the liquid crystal display of the invention isapplied to a liquid crystal display using an ECB or TN liquid crystallayer containing nematic liquid crystal material having positivedielectric anisotropy. In addition, it is preferable that the liquidcrystal layer included in each of the sub pixels has ECB and TN modes ofa multi-domain including two to four domains having different azimuthangles at which the liquid crystal molecules are inclined underapplication of a voltage. Details of modes of the multi-domain aredisclosed in JP-A-9-160042.

The liquid crystal display of the invention is effective for an OCBmode, a VA mode, a HAN mode, and a STN mode in addition to theabove-described display mode.

The liquid crystal display of the invention is not limited to theconfiguration shown in FIG. 10, but may include other members. Forexample, a color filter may be interposed between the liquid crystalcell and the polarizer. In addition, a separate optical compensationfilm may be interposed between the liquid crystal cell and thepolarizing plate, which will be described later. In addition, in case ofa transmission type liquid crystal display, a backlight unit having alight source such as a cold cathode or hot cathode fluorescent tube, alight emitting diode, a field emission device, or an electroluminescencedevice may be disposed behind the liquid crystal cell. In addition, theliquid crystal display of the invention may be of a reflection type. Inthis case, only one polarizing plate may be disposed at an observationside, and a reflecting film is disposed behind the liquid crystal cellor at an inner side of the lower substrate of the liquid crystal cell.Of course, a front light unit using the light source may be provided ata liquid crystal cell observation side.

The liquid crystal display of the invention includes image direct-viewtype, image projection type and light modulation type display devices.In addition, although the liquid crystal display employing TFT deviceshas been illustrated in the above, other switching devices (for example,MIM devices) may be employed. The invention is particularly effectivefor an active matrix liquid crystal display using three or two terminalsemiconductor devices such as TFT or MIM. Of course, the invention isalso effective for a passive matrix liquid crystal display representedby a STN type which is called a time division driving.

In addition, an optical compensation film having an opticallyanisotropic layer formed using a hybrid alignment of disk-like liquidcrystal molecules usable in the invention is disclosed inJP-A-2000-304930 (paragraphs (0014) to (0141)) and may be applied to theliquid crystal display of the invention.

According to still another aspect (IV), the invention provides a liquidcrystal display comprising a pair of polarizing plates, each including apolarizer and a transparent layer, transmission axes of the polarizerand the transparent layer being perpendicular to each other, and aliquid crystal panel interposed between the pair of polarizing plates,wherein the liquid crystal panel includes a pair of opposite substrates,at least one of which has an electrode, a liquid crystal layer includingliquid crystal molecules aligned by alignment axes of opposite surfacesof the pair of opposite substrates, and at least one pair of opticallyanisotropic layers with the liquid crystal layer interposed between theat least one pair of optically anisotropic layers, wherein the liquidcrystal panel has a double symmetrical axis with regard to a cubicstructure formed in upper and lower alignment control directions of theliquid crystal layer which are defined by the alignment axes of oppositesurfaces of the pair of opposite substrates and alignment controldirections of the pair of optically anisotropic layers, the doublesymmetrical axis being in parallel to the surfaces of the substrates, atransmission axis of one of the pair of polarizing plates is in parallelto the double symmetrical axis, and a transmission axis of the other ofthe pair of polarizing plates is perpendicular to the double symmetricalaxis, and wherein a transparent layer, which is interposed between theliquid crystal layer and the polarizer, of the transparent layersincluded in the pair of polarizing plates is a biaxial retardationlayer, in-plane retardation of the retardation layer is 250 to 300 nm,an NZ value of the retardation layer is 0.1 to 0.4, and an in-planeretardation axis of the retardation layer is perpendicular to anabsorption axis of the polarizer closer to the retardation layer.

According to still another aspect, the invention provides a liquidcrystal display comprising a pair of polarizing plates, each including apolarizer and a transparent layer, transmission axes of the polarizerand the transparent layer being perpendicular to each other, and aliquid crystal panel interposed between the pair of polarizing plates,wherein the liquid crystal panel includes a pair of opposite substrates,at least one of which has an electrode, a liquid crystal layer includingliquid crystal molecules aligned by alignment axes of opposite surfacesof the pair of opposite substrates, and at least one pair of opticallyanisotropic layers with the liquid crystal layer interposed between theat least one pair of optically anisotropic layers, wherein the liquidcrystal panel has a double symmetrical axis with regard to a cubicstructure formed in upper and lower alignment control directions of theliquid crystal layer which are defined by the alignment axes of oppositesurfaces of the pair of opposite substrates and alignment controldirections of the pair of optically anisotropic layers, the doublesymmetrical axis being in parallel to the surfaces of the substrates, atransmission axis of one of the pair of polarizing plates is in parallelto the double symmetrical axis, and a transmission axis of the other ofthe pair of polarizing plates is perpendicular to the double symmetricalaxis, and wherein a transparent layer, which is interposed between theliquid crystal layer and the polarizer, of the transparent layersincluded in the pair of polarizing plates is a biaxial retardationlayer, in-plane retardation of the retardation layer is 250 to 300 nm,an NZ value of the retardation layer is 0.6 to 1.1, and an in-planeretardation axis of the retardation layer is in parallel to anabsorption axis of the polarizer closer to the retardation layer, or aliquid crystal display comprising a pair of polarizing plates, eachincluding a polarizer and a transparent layer, transmission axes of thepolarizer and the transparent layer being perpendicular to each other,and a liquid crystal panel interposed between the pair of polarizingplates, wherein the liquid crystal panel includes a pair of oppositesubstrates, at least one of which has an electrode, a liquid crystallayer including liquid crystal molecules aligned by alignment axes ofopposite surfaces of the pair of opposite substrates, and at least onepair of optically anisotropic layers with the liquid crystal layerinterposed between the at least one pair of optically anisotropiclayers, wherein the liquid crystal panel has a double symmetrical axiswith regard to a cubic structure formed in upper and lower alignmentcontrol directions of the liquid crystal layer which are defined by thealignment axes of opposite surfaces of the pair of opposite substratesand alignment control directions of the pair of optically anisotropiclayers, the double symmetrical axis being in parallel to the surfaces ofthe substrates, a transmission axis of one of the pair of polarizingplates is in parallel to the double symmetrical axis, and a transmissionaxis of the other of the pair of polarizing plates is perpendicular tothe double symmetrical axis, and wherein a transparent layer, which isinterposed between the liquid crystal layer and the polarizer, of thetransparent layers included in the pair of polarizing plates has abiaxial retardation function, and an in-plane retardation axis of thetransparent layer is in parallel to a transmission axis of the polarizercloser to the retardation layer.

In addition, according to still another preferred aspect, the inventionprovides a liquid crystal display comprising a pair of polarizingplates, each including a polarizer and a transparent layer, transmissionaxes of the polarizer and the transparent layer being perpendicular toeach other, and a liquid crystal panel interposed between the pair ofpolarizing plates, wherein the liquid crystal panel includes a pair ofopposite substrates, at least one of which has an electrode, a liquidcrystal layer including liquid crystal molecules aligned by alignmentaxes of opposite surfaces of the pair of opposite substrates, and atleast one pair of optically anisotropic layers with the liquid crystallayer interposed between the at least one pair of optically anisotropiclayers, wherein the liquid crystal panel has a double symmetrical axiswith regard to a cubic structure formed in upper and lower alignmentcontrol directions of the liquid crystal layer which are defined by thealignment axes of opposite surfaces of the pair of opposite substratesand alignment control directions of the pair of optically anisotropiclayers, the double symmetrical axis being in parallel to the surfaces ofthe substrates, a transmission axis of one of the pair of polarizingplates is in parallel to the double symmetrical axis, and a transmissionaxis of the other of the pair of polarizing plates is perpendicular tothe double symmetrical axis, and wherein a transparent layer, which isinterposed between the liquid crystal layer and the polarizer, of thetransparent layers included in the pair of polarizing plates has anin-plane retardation axis in parallel to a transmission axis of thepolarizer closer to the retardation layer, and assuming that in-planeretardation of the transparent layer is Re and thickness directionretardation of the transparent layer is Rth, Rth of the transparentlayer for a wavelength of 550 nm is 70 to 400 nm, Re of the transparentlayer for the same wavelength is 20˜80 nm, a ratio of Re to Rth (Re/Rth)for a wavelength of 450 nm is 0.4 to 0.95 times a ratio of Re to Rth(Re/Rth) for a wavelength of 550 nm, and Re/Rth for a wavelength of 650nm is 1.05 to 1.9 times Re/Rth for a wavelength of 550 nm.

According to the above aspects, by adjusting an arrangement anglerelationship between the polarizing plate absorption axis (ortransmission axis), the alignment control direction of the liquidcrystal layer, and the alignment control direction of the opticallyanisotropic layer having the optical compensation performance andinterposing a transparent layer having an optical characteristic betweenthe polarizing plate and the liquid crystal panel, there can be provideda liquid crystal display, particularly a TN mode liquid crystal display,with high reliability and good display quality in vertical andhorizontal viewing angles even under severe use environments, with thesame configuration as the conventional liquid crystal display.

Hereinafter, the above aspect (IV) of the invention will be described indetail.

In the invention, for a liquid crystal display having a pair ofpolarizing plates and a liquid crystal cell interposed between the pairof polarizing plates, by making absorption axes of polarizers includedin the pair of polarizing plates substantially parallel or perpendicularto a maximal contraction direction of the polarizing plates, that is,long and short side directions (or horizontal direction of a screen ofthe display device) of an end portion of the polarizing plates, light isno or little leaked out of circumferences of the polarizing plates evenunder severe use environments (high temperature and high humidity), forexample, even under use environments of temperature of 40° C. andhumidity of 90% or temperature of 65° C. and humidity of 80%. Inaddition, deterioration of a viewing angle characteristic, which mayoccur due to such arrangement, can be avoided by adjusting anarrangement angle relationship between the alignment control directionof the liquid crystal layer and the alignment control direction of theoptically anisotropic layer, thereby satisfying a required wide viewingangle characteristic.

The prevent inventors have discovered that light leakage out ofcircumferences of polarizing plates in conventional TN mode liquidcrystal displays is caused by retardation Re and Rth generated inpolarizing plate protective films due to a photoelastic effect bycontraction of the polarizing plates. Based on this discover, thepresent inventor have also discovered that the light leakage can bedecreased by adjusting an arrangement angle relationship between thealignment control direction of the liquid crystal layer, the alignmentcontrol direction of the optically anisotropic layer for opticalcompensation, and the absorption of the polarizing plates.

The polarizing plates are contracted under severe environments.Particularly, contraction in a direction in parallel to long and shortsides of a screen becomes maximal. When an elastic force such ascontraction or expansion is applied to a film used in the polarizingplates, retardation is changed. In a configuration where an absorptionaxis of the polarizing plate intersects a generation direction of theretardation by 45°, light transmission becomes maximal, which isobserved as light leakage. In the invention, with the above describedarrangement, observed light leakage is reduced.

The invention is remarkably effective for a TN mode liquid crystallayer. In a conventional TN mode liquid crystal layer, an absorptionplate absorption axis intersects a horizontal direction of a screen,that is, a long side direction of an end portion of a polarizing plateby 45°. Since a contraction direction of the polarizing plate is inparallel to long and short directions of the end portion of thepolarizing plate, such a conventional arrangement gives the maximallight leakage. Accordingly, in the invention, by making a pair ofpolarizing plate absorption axes parallel or perpendicular to thehorizontal direction of the screen, that is, the long side direction ofthe end portion of the polarizing plate, light leakage can be decreasedin the TN mode.

The TN mode liquid crystal display employs a TFT driving in order todisplay a high quality image having high contrast high precision. Forthe TFT driving, gate wiring lines and signal (or source) wiring linesare arranged in horizontal and vertical directions of a screen. Since acontraction direction of a polarizing plate is in parallel orperpendicular to these wiring lines, even if a polarizing plateabsorption axis is arranged in parallel or perpendicular to these wiringlines, the absorption axis is arranged in substantial parallel orperpendicular to the maximal contraction direction of the polarizingplate, that is, long and short side directions of an end portion of thepolarizing plate, thereby decreasing light leakage.

In addition, the TN mode liquid crystal display, in order to obtain awide viewing angle characteristic, it is preferable that the absorptionaxis of at least one of the pair of polarizing plates intersects thealignment axis formed at a plane opposite to the liquid crystal cellsubstrate arranged at a side of at least one of the polarizing plates byabout 45°.

Light leakage out of circumferences of the polarizing plate can bedecreased by making the polarizing plate absorption axis parallel orperpendicular to the long side direction of the end portion of thepolarizing plate. At this time, by inclining an alignment controldirection of the TN mode liquid crystal display, that is, an alignmentaxis formed at an opposite side of a substrate of a liquid crystal cell,by 45° with respect to the horizontal direction of the screen, asubstantially bilateral symmetrical viewing angle characteristic can beobtained. In the conventional TN mode, the alignment control directionof the liquid crystal cell is inclined by 45° with respect to thehorizontal direction of the screen, and a vertical viewing anglecharacteristic is asymmetrical while the horizontal viewing anglecharacteristic is symmetrical. However, since the polarizing plateabsorption axis and a retardation axis of a protective film of thepolarizing plate are also inclined by 45° with respect to the horizontaldirection of the screen, light is leaked out of the circumference of thepolarizing plate under severe use environments.

Prior to description of the invention, an operation of a liquid crystaldisplay in the background art, shown in FIG. 15, will be described byway of example of a general TN mode. Here, using nematic liquid crystalshaving positive dielectric anisotropy as field effect liquid crystals, aTFT (active) driving will be described by way of an example. A liquidcrystal display in the background art comprises a liquid crystal cellhaving an upper substrate 457, a lower substrate 460, and a liquidcrystal layer having liquid crystal molecules 459 interposed betweenthese substrates. Alignment films (not shown) are formed on surfaces ofthe substrates 457 and 460 contacting the liquid crystal molecules 459(hereinafter, these surfaces are sometimes referred to as “innersurfaces”), and alignment of the liquid crystal molecules 459 underapplication of no voltage or application of a low voltage is controlledby a rubbing treatment to which the alignment films are subjected. Inaddition, transparent electrodes (not shown) that apply a voltage to theliquid crystal layer having the liquid crystal molecules 459 are formedon the inner surfaces of the substrates 457 and 460.

An upper polarizing plate comprises an upper polarizer 451 and aprotective film 453 for protecting the upper polarizer 451, and a lowerpolarizing plate comprises a lower polarizer 466 and a protective film464 for protecting the lower polarizer 466. These polarizing platesgenerally have another protective film in the outside thereof, althoughit is not shown in FIG. 15. As shown in FIG. 15, in the conventionalliquid crystal display, an absorption axis 452 of the upper polarizer451 is substantially perpendicular to an absorption axis 467 of thelower polarizer 466 in a 45° direction with respect to a horizontaldirection of a screen (direction a in the figure). In addition, theabsorption axis 452 of the upper polarizing plate is substantiallyperpendicular to a rubbing direction (alignment axis) 458 of the uppersubstrate 457, and the absorption axis 467 of the lower polarizing plateis substantially perpendicular to a rubbing direction (alignment axis)461 of the lower substrate 460. In addition, in order to removeretardation by the liquid crystal molecules 459, optically anisotropiclayers 455 and 462 are interposed between the upper and lower polarizingplates and the liquid crystal cell, respectively. The opticallyanisotropic layers 455 and 462 are formed of a liquid crystalcomposition containing, for example, a discotic liquid crystal compound,and, average alignment directions 456 and 463 of discotic moleculesfixed in the optically anisotropic layers 455 and 462 are in substantialparallel to the rubbing axes 458 and 461 of the liquid crystal cellsubstrates 457 and 460 located closer than the optically anisotropiclayers 455 and 462, respectively.

In the TN type liquid crystal display, under a non-driving state where adriving voltage is not applied to the electrodes, the liquid crystalmolecules 459 in the liquid crystal cell are aligned in substantialparallel to substrate planes and alignment direction is twisted by 90°between the upper and lower substrates 457 and 460. In case of atransmission type display device, light emitted from a backlight unithas linear polarization after passing through the lower polarizer 466.The linearly polarized light propagates along the twisted structure ofthe liquid crystal layer, rotates a polarizing plane by 90°, and thenpasses through the upper polarizer 451. Accordingly, the display devicedisplays a white image.

On the other hand, when an application voltage is increased, the liquidcrystal molecules 457 get stand perpendicularly to the substrate planeswhile being untwisted. In the TN type liquid crystal display underapplication of an ideal high voltage, the liquid crystal molecules 457are nearly completely untwisted, and, accordingly, have a state ofalignment nearly perpendicular to the substrate planes. At this time,since there is no twisted structure in the liquid crystal layer, thelinearly polarized light that passed through the lower polarizer 466propagates without rotating the polarizing plane and is perpendicularlyincident into the absorption axis 452 of the upper polarizer 451.Accordingly, the light is shielded and the display device displays ablack image. However, in a driving state, since the liquid crystalmolecules 457 are aligned by an angle with respect to the substratesurface, retardation occurs. This retardation is alleviated by theoptical compensation layers 455 and 462, thereby obtaining an idealblack image display in the driving state.

In this manner, the TN type liquid crystal display achieves a functionas a display device by shielding or transmitting the polarized light. Ingeneral, a contrast ratio as a numerical value to indicate displayquality is defined by a ratio of white display luminance to blackdisplay luminance. A higher contrast ratio gives a higher qualitydisplay device. In order to increase a contrast ratio, it is importantto maintain a polarization state in a liquid crystal display.

However, as described above, when the conventional liquid crystaldisplay is used under severe environments such as high temperature andhigh humidity, there arises a problem in that the polarizing plate iscontracted, and accordingly, light is leaked out of a circumference ofthe polarizing plate. The present inventors have paid attention tosymmetry of a cubic structure formed in upper and lower alignmentcontrol directions of a liquid crystal layer defined by an alignmentaxis of opposite planes of a pair of substrates for a liquid crystalcell and alignment control directions of a pair of upper and loweroptically anisotropic layers and have found that the above problem canbe overcome based on the fact that the cubic structure has a doublesymmetrical axis in a plane in parallel to a substrate surface, andabsorption axes of a pair of upper and lower polarizing plates have arelationship with the double symmetrical axis.

To begin with, the concept of the double symmetrical axis and the cubicstructure that is formed in the upper and lower alignment controldirections of the liquid crystal layer forming a liquid crystal paneland the alignment control directions of the upper and lower opticallyanisotropic layers and has the double symmetrical axis will be describedby way of an example. FIG. 16 shows a liquid crystal alignment directionof the liquid crystal layer forming the liquid crystal panel of theconventional TN type liquid crystal display shown in FIG. 15 andabsorption axis directions of the polarizing plates with the liquidcrystal layer interposed therebetween. In FIG. 16, in the liquid crystallayer, although a director in the liquid crystal layer is changed suchthat the liquid crystal molecules are aligned to be untwisted along anelectric field direction depending on an applied voltage, the alignmentcontrol directions defined by the alignment axis (for example, rubbingaxis) of the opposite plane of the upper and lower substrates fixing thealignment (in the specification, sometimes referred to as “upper andlower alignment control directions of the liquid crystal layer”) arefixed with a pretilt angle (for example, 4° or so) tilted from thesubstrate surface, and a difference between the upper and loweralignment control directions of the liquid crystal layer. As shown inFIG. 16, when a structure of “liquid crystal+polarizing plate” isrotated by 180° with a C2 axis, which is indicated by an arrow, as arotation axis, this structure is completely the same as a structurebefore rotation. This is referred to that the cubic structure has adouble rotation axis (double symmetrical axis). It is here noted thatthe cubic structure considers only a factor used to actively relate thestructure to a switching by birefringence of light, which is theprinciple of a liquid crystal display. The factor may include, forexample, the liquid crystal layer, the polarizing plate, a retardationplate, etc. For example, it is not considered whether or not membershaving small birefringence, such as a color filter, an anti-reflectionfilm, a scattering layer and the like, used for a different purpose arecompletely the same after and before rotation.

When the cubic structure has such a double symmetrical axis, the liquidcrystal panel has a bilateral symmetry in a C2 axis direction. Thereason for this is as follows. In the left figure of FIG. 17, light thattransmits from the right front side to the left inner side has the sametransmittance as light that transmits from the left inner side to theright front side. Similarly, light that transmits from the right upperfront side to the left lower inner side has the same transmittance aslight that transmits from the left lower inner side to the right upperfront side. When the liquid crystal panel is rotated by 180° around theC2 axis, the cubic structure before rotation is the same as the cubicstructure after rotation since the liquid crystal panel has the doublesymmetrical axis. In addition, the right front side just before moves tothe left inner side, the left inner side moves the right front side, theright upper front side moves the left upper inner side, and the leftlower inner side moves the right lower front side. As can be seen fromthe figures before and after rotation, the transmittance in the rightdirection becomes equal to the transmittance in the left direction, andthe transmittance in the right upper direction becomes equal to thetransmittance in the left upper direction. That is, a bilateralsymmetrical transmittance characteristic is obtained. This means thatthe cubic structure having the double symmetrical axis has a symmetrycharacteristic in the symmetrical axis direction. It is well known thata typical TN type liquid crystal display panel has a bilateral symmetrycharacteristic since the panel has a double symmetrical axis in left andright directions.

This relationship is also established when a voltage is applied to theliquid crystal layer. In addition, this relationship is also establishedfor a liquid crystal display having a TN type liquid crystal panelincluding an optically anisotropic layer formed of a discotic compoundconventionally used for optical compensation. In other words, thebilateral symmetry is a special feature of the conventional liquidcrystal display. However, in the invention, the absorption axes of thepolarizing plates are arranged in the vertical and horizontal directionsof the screen. This configuration is schematically shown in FIG. 18.

A TN liquid crystal panel of the invention shown in FIG. 18 is differentin absorption axis directions of upper and lower polarizing plates fromthe conventional TN liquid crystal panel shown in FIG. 17. Accordingly,in the TN liquid crystal panel shown in FIG. 18, a cubic structure ofliquid crystal+polarizing plate” has no double rotation axis. This isbecause the upper and lower polarizing plates has no double symmetricalaxis although the liquid crystal panel without the polarizing plates hasthe double symmetrical axis. Accordingly, this cubic structure can notobtain a bilateral symmetry characteristic. The invention ischaracterized in that the cubic structure has bilateral symmetry, forexample, the right upper side having the same characteristic as the leftupper side, the right lower side having the same characteristic as theleft lower side. In other words, in a structure where a liquid crystalpanel having a double symmetrical axis is interposed betweenperpendicular polarizing plates, when one absorption axis (ortransmission axis) of the perpendicular polarizing plates is in parallelto the double symmetrical axis of the liquid crystal panel, a liquidcrystal display having symmetrical transmittance in a planeperpendicular to a double symmetrical axis direction of the liquidcrystal panel is attained. Specifically, in the invention, the abovestructure is attained by interposing a phase difference layer indicatinga birefringence between the liquid crystal panel and the perpendicularpolarizing plates, which will be described in detail below.

As shown in FIG. 18, the completely same characteristic is obtained inthe left and right directions, that is, a 0° direction and a 180°direction. However, the same characteristic is not obtained in the rightinclined upper direction, for example, a 30° direction, and the leftinclined upper direction, for example, a 150° direction. That is, abilateral symmetry is not obtained in the right inclined direction andthe left inclined direction. The present inventors have deliberated howto apply the fact that the completely same characteristic is obtained inthe left and right directions to the inclined upper direction or theinclined lower direction. The reason why the completely samecharacteristic is obtained in the left and right directions is that onlythe axis is changed between upper and lower directions, with theperpendicular relationship of the polarizing plates before and afterrotation of the C2 symmetry unchanged in FIG. 18. The reason for suchsame characteristic may be described as follow.

First, a Jones matrix of an anisotropic medium can be expressed by thefollowing equation.

$M = \begin{pmatrix}{a + {ib}} & {c + {id}} \\{{- c} + {id}} & {a - {id}}\end{pmatrix}$

Where, a, b, c and d are real numbers, and a²+b²+c²+d²=1. Assuming thatan x axis is a 0° direction and a y axis is a 90° direction, when theanisotropic medium is inserted between a lower polarizing plate havingthe x axis as a transmission axis and an upper polarizing plate havingthe y axis as a transmission axis, transmittance is expressed by thefollowing equation.

$T = {{\begin{matrix}\begin{pmatrix}0 & 1\end{pmatrix} & \begin{pmatrix}{a + {id}} & {c + {id}} \\{{- c} + {id}} & {a + {ib}}\end{pmatrix} & \begin{pmatrix}1 \\0\end{pmatrix}\end{matrix}} = {c^{2} + d^{2}}}$

On the other hand, when the anisotropic medium is inserted between alower polarizing plate having the y axis as a transmission axis and anupper polarizing plate having the x axis as a transmission axis,transmittance is expressed by the following equation.

$T = {{\begin{matrix}\begin{pmatrix}0 & 1\end{pmatrix} & \begin{pmatrix}{a + {id}} & {c + {id}} \\{{- c} + {id}} & {a + {ib}}\end{pmatrix} & \begin{pmatrix}1 \\0\end{pmatrix}\end{matrix}} = {c^{2} + d^{2}}}$

That is, Equations above have the same transmittance. In other words,changing only a polarizing direction between the upper and lowerdirections without collapsing the perpendicular relationship gives thesame characteristic. This is the reason why the completely samecharacteristic is obtained in the left and right directions. The presentinventors have deliberated how to apply the fact that the completelysame characteristic is obtained in the left and right directions to theinclined directions and have found that the above asymmetry problem canbe overcome by arranging a C2 symmetrical liquid crystal panel between apair of polarizing plates with polarizing axes perpendicular to eachother in an inclined direction.

Specifically, according to one aspect of the invention, a pair ofpolarizing plates includes a polarizer and a biaxial retardation layer.The biaxial retardation layer is interposed between a liquid crystalpanel and the polarizer, in-plane retardation of the retardation layeris 250 to 300 nm, and an NZ value has a birefringence characteristic of0.1 to 0.4. In this aspect, an in-plane retardation axis of theretardation layer is arranged perpendicular to an absorption axis of thepolarizer arranged closer to the retardation layer.

In addition, according to another aspect of the invention, a pair ofpolarizing plates includes a polarizer and a biaxial retardation layer.In-plane retardation of the retardation layer is 250 to 300 nm, and anNZ value has a birefringence characteristic of 0.6 to 1.1. In thisaspect, an in-plane retardation axis of the retardation layer isarranged perpendicular to an absorption axis of the polarizer arrangedcloser to the retardation layer.

The above two aspects will be described below using a Poincare sphere. APoincare sphere shown in FIG. 19 is a diagram of an orthogonalprojection of S1 and S3 having an azimuth angle of 45° and a polar angleof 60°. When linearly polarized light that passed a polarizer of onepolarizing plate passes the retardation layer, a polarizing axis movesto a point of S1=S3=0. Since the other polarizing plate includes theretardation layer, the two polarizing plates remain perpendicular toeach other in an inclined direction. Since only a vertical relationshipis changed with the perpendicular relationship unchanged although thepolarizing plates are rotated around the C2 symmetrical axis of theliquid crystal panel, it can be seen that this relationship is acondition of obtaining the symmetry characteristic as described above.Details of the biaxial retardation layer used in the above two aspectsand change of polarizing state of incident light of the retardationlayer are disclosed in JP-A-2001-350022, the disclosure of which isincorporated herein by reference.

In addition, in the above two aspects, a uniaxial retardation layer maybe interposed between the retardation layer and the liquid crystalpanel. The bilateral symmetry is also obtained in a configuration wherean optical axis of the uniaxial retardation layer is disposedperpendicular to the layer. A locus of polarizing state on the Poincaresphere in this aspect is shown in FIG. 20. FIG. 20 shows a polarizingstate when a λ/2 plate having an Nz value of 0.25 is used as the biaxialretardation layer and C-plates having the same optical characteristicare interposed between an upper polarizing plate and the liquid crystalpanel and between a lower polarizing plate and the liquid crystal panel,respectively. As shown in the figure, in this aspect, the doublesymmetry of the liquid crystal panel is not collapsed. Accordingly, itis understood that the bilateral symmetry characteristic is obtained forthe above described reason. The retardation of the used C-plate israndom. The bilateral symmetry is obtained at any retardation values. Inorder to cancel the retardation of the liquid crystal layer, Rth is,preferably, 0 to 300 nm, more preferably, 0 to 200 nm, particularlypreferably, 0 to 100 nm. Details of the C-plate used in this aspect aredisclosed in JP-A-62-210423, the disclosure of which is incorporatedherein by reference.

According to still another aspect of the invention, there is provided aliquid crystal display in which a transparent layer, which is interposedat least between the liquid crystal layer and the polarizer, oftransparent layers of the pair of polarizing plates has a biaxialretardation function, and an in-plane retardation axis of thetransparent layer is in parallel to a transmission axis of the polarizerarranged closer to the retardation layer. A locus of polarizing state onthe Poincare sphere in this aspect is shown in FIG. 21. In this aspect,by using a film having the biaxial retardation function (sometimesreferred to as “biaxial film”), change of the polarizing state as shownin FIG. 21 is possible. More specifically, a biaxial film by which thepolarizing state can be changed on a line of S1=0 in the figure is used.In this aspect, it is understood that the bilateral symmetry can beobtained. The in-plane retardation axis of the biaxial film is inparallel to the transmission axis of the adjacent polarizer. An exampleof the biaxial film may include, preferably, a film having thicknessdirection retardation of 70 to 400 nm and in-plane retardation of 20 to80 nm, more preferably, a film having thickness direction retardation of100 to 300 nm and in-plane retardation of 20 to 70 nm, particularlypreferably, a film having thickness direction retardation of 110 to 280nm and in-plane retardation of 30 to 70 nm, for a wavelength of 550 nm

According to still another aspect of the invention, a transparent layer,which is interposed at least between the liquid crystal layer and thepolarizer, of transparent layers of the pair of polarizing plates has awavelength dispersion characteristic. More specifically, assuming thatthe in-plane retardation of the transparent layer is Re and thethickness direction retardation is Rth, Re/Rth for a wavelength λ of 450nm in a visible light region is 0.4 to 0.95 times Re/Rth for awavelength λ of 550 nm, and Re/Rth for a wavelength λ of 650 nm is 1.05to 1.9 times Re/Rth for a wavelength λ of 550 nm. FIG. 22 shows a locusof the polarizing state on the Poincare sphere in this aspect. As can beseen from the figure, the biaxial film used as the transparent layer haswavelength dispersion adjusted for any light of R, G and B wavelengths.That is, the polarizing state moves to the line of S1=0 for any light ofR, G and B wavelengths. In this aspect, it is understood that thecompletely bilateral symmetry is obtained for any of R, G and Bwavelengths in the visible light region.

In any of the above aspects, the liquid crystal panel includes the pairof optically anisotropic layers with the liquid layer interposedtherebetween. For example, if the liquid crystal layer has a TN mode, itis preferable that alignment of the pair of optically anisotropic layersof the liquid crystal panel is controlled by the alignment axis and thepair of optically anisotropic layers is a layer containing a liquidcrystal compound with the alignment state fixed. In this aspect, it ispreferable that an intersection angle between the alignment controldirection of the optically anisotropic layers defined by the alignmentaxis such as a rubbing axis and at least one of alignment controldirections of the liquid crystal layer falls within a range of 0° to10°. Particularly, a TN mode liquid crystal layer can be opticallyeffectively compensated within this range.

According to still another aspect of the invention, the liquid crystalpanel includes the pair of optically anisotropic layers (a pair of firstoptically anisotropic layers) and a pair of second optically anisotropiclayers. In this aspect, it is expected to obtain a preferred effect ofsuppressing color jump in a halftone, which may occur due tointersection of absorption axes of the pair of polarizing plates in a0-90° direction. In this aspect, the liquid crystal layer is interposedbetween the pair of first optically anisotropic layers, and the pair ofsecond optically anisotropic layers is arranged with the pair of firstoptically anisotropic layers interposed therebetween. It is preferablethat alignment of the pairs of first and second optically anisotropiclayers is controlled by the alignment axis such as the rubbing axis andthe pairs of first and second optically anisotropic layers are a layercontaining a liquid crystal compound with the alignment state fixed. Inorder to obtain the preferred effect of suppressing the color jump inthe halftone, it is preferable that an intersection angle between thealignment control direction of the first optically anisotropic layersand at least one of alignment control directions of the liquid crystallayer falls within a range of 0° to 10° and an intersection anglebetween the alignment control direction of the second opticallyanisotropic layers and at least one of alignment control directions ofthe liquid crystal layer is about 45°.

FIG. 14 shows an example of a configuration of the liquid crystaldisplay of the invention. This example is merely used to explain theeffect of the invention, and the invention is not limited to thisexample. Here, using nematic liquid crystals having positive dielectricanisotropy as field effect liquid crystals, a TFT (active) driving willbe described by way of an example.

The TN mode liquid crystal display shown in FIG. 14 comprises a liquidcrystal cell having an upper substrate 407, a lower substrate 410, and aliquid crystal layer having liquid crystal molecules 409 interposedbetween these substrates. Alignment films (not shown) are formed onsurfaces of the substrates 407 and 410 contacting the liquid crystalmolecules 409 (hereinafter, these surfaces are sometimes referred to as“inner surfaces”), and alignment of the liquid crystal molecules 409under application of no voltage or application of a low voltage iscontrolled by a rubbing treatment to which the alignment films aresubjected. In addition, transparent electrodes (not shown) that apply avoltage to the liquid crystal layer having the liquid crystal molecules409 are formed on the inner surfaces of the substrates 407 and 410. Inaddition, a pair of first upper and lower optically anisotropic layers405 a and 412 a and a pair of second upper and lower opticallyanisotropic layers 405 b and 412 b are disposed with the liquid crystalcell interposed therebetween. In the liquid crystal display shown inFIG. 14, a liquid crystal panel Lp is constituted by the liquid crystalcell, the pair of first upper and lower optically anisotropic layers 405a and 412 a and the pair of second upper and lower optically anisotropiclayers 405 b and 412 b. In addition, a pair of upper and lowerpolarizers 401 and 416 is disposed with the liquid crystal panel Lpinterposed therebetween. Absorption axes 402 and 417 of the polarizers401 and 416 have 90° (perpendicular) and 0° (parallel) with respect to ahorizontal direction of a screen, thereby reducing light leakage out ofcircumferences of the polarizers, which occurs due to contraction of thepolarizers under severe use environments.

The first upper and lower optically anisotropic layers 405 a and 412 aand the second upper and lower optically anisotropic layers 405 b and412 b included in the liquid crystal panel Lp are formed of acomposition containing a liquid crystal compound, and molecules of theliquid crystal compound in the layers are fixedly aligned in thealignment control directions defined by the alignment axis such as therubbing axis. An intersection angle between the alignment controldirections 406 a and 413 a of the first optically anisotropic layers andat least one of the alignment control directions 408 and 411 of theliquid crystal layer falls within a range of 0° to 10° (preferably 0°)and an intersection angle between the alignment control directions 406 band 413 b of the second optically anisotropic layers and one of thealignment control directions 408 and 411 of the liquid crystal layer isabout 45°. It is preferable that an intersection angle between thealignment control directions of the optically anisotropic layers and thealignment control directions defined by a plane opposite the substratedisposed closer to the optically anisotropic layers falls with the aboverange (for example, an intersection angle between alignment controldirections of the optically anisotropic layers 405 a and 405 b andalignment control directions of the liquid crystal layer defined by thealignment axis 408 such as the rubbing axis formed on the plane oppositeto the substrate 407 falls within the above range, and an intersectionangle between alignment control directions of the optically anisotropiclayers 412 a and 412 b and alignment control directions of the liquidcrystal layer defined by the alignment axis 411 such as the rubbing axisformed on the plane opposite to the substrate 410 falls within the aboverange). An alignment control direction of an optically anisotropic layerrefers to an average alignment direction of a molecule symmetrical axisof molecules in the optically anisotropic layer. In general, thealignment control direction is defined by a direction of rubbingtreatment to which an alignment film used when the optically anisotropiclayer is formed is subjected.

In addition, in the invention, it is preferable that the first opticallyanisotropic layer and the second optically anisotropic layer disposed asnecessary are layers formed by fixing a liquid crystal compositioncontaining a discotic liquid crystal compound in a hybrid alignmentstate.

It is here important that the liquid crystal panel Lp (interposedbetween the pair of second optically anisotropic layers in FIG. 14) hasthe double symmetrical axis in parallel to the surface of the substrate.One of the pair of polarizing plates with the liquid crystal panel Lpinterposed therebetween is the upper polarizing plate including thepolarizer 401 and the transparent layer 403, and the other is thepolarizing plate including the polarizer 416 and the transparent layer414. The absorption axes 402 and 417 of the polarizing plates are inparallel or perpendicular to the double symmetrical axis of the liquidcrystal panel. With this configuration, the bilateral symmetry isobtained. In addition, in this aspect, by controlling the polarizingstate of light incident from the outside of the upper and lowerpolarizing plates using optical characteristics of the transparentlayers 403 and 414 according to the methods shown in FIGS. 19 to 22, asymmetry characteristic is also obtained in an inclined right upper 45°direction and an inclined left upper 45° direction. For example,polarization after polarized light incident from the outside in theinclined right upper 45° direction of the upper polarizing plate passesthe transparent layer 403 and polarization of light incident in theupper front direction of the upper polarizing plate have the sameelliptical polarizing state as in the long side direction of thepolarization. Similarly, polarization after polarized light incidentfrom the outside in the inclined left lower 45° direction of the lowerpolarizing plate passes the transparent layer 414 and polarization oflight incident in the lower front direction of the lower polarizingplate have the same elliptical polarizing state as in the long sidedirection of the polarization. In this manner, the pair of polarizingplates is perpendicular to an elliptical polarizing axis in inclinedupper and lower directions as well as the right and left directions,thereby obtaining symmetry in all of the inclined upper and lowerdirections and the right and left directions.

The TN mode liquid crystal display shown in FIG. 14 has the sameoperation principle as the conventional liquid crystal display shown inFIG. 15. Hereinafter, an example of a configuration of a TN mode liquidcrystal cell usable for the liquid crystal display shown in FIG. 14 willbe described. A liquid crystal cell is manufactured by rubbing andaligning liquid crystals having positive dielectric anisotropy,anisotropic refractive index Δn=0.0854 (589 nm, 20° C.), and Δ∈=+8.5,and is disposed between the upper and lower substrates 407 and 410. Thealignment of the liquid crystal layer is controlled by the alignmentfilm and the rubbing treatment. A director, a so-called tilt angle,indicating the alignment direction of the liquid crystal molecules isset to falls within a range of, preferably, about 0.1° to 10°. In thisembodiment, the director is set to be 3°. The rubbing treatment isperformed in a direction perpendicular to the upper and lowersubstrates, and the size of the tilt angle can be controlled by rubbingstrength and number. The alignment films are formed by applying andfiring a polyimide film. The size of a twist angle of the liquid crystallayer is defined by an intersection angle in a rubbing direction betweenthe upper, and lower substrates and a chiral agent added to liquidcrystal material. In this embodiment, a chiral agent having a pitch of60 μm or so is added so that the twist angle is about 90°. The thicknessd of the liquid crystal layer is set to be 5 μm.

In addition, liquid crystal material LC is not particularly limited aslong as it is nematic liquid crystal. As dielectric anisotropy Δ∈increases, the driving voltage can be further reduced. As refractiveindex anisotropy Δn decreases, the thickness (gap) of the liquid crystallayer can be further thickened, thereby shortening time taken to injectand seal liquid crystals and reducing unbalance of the gap. In addition,as Δn increases, a cell gap can be further decreased, thereby allowing ahigher speed response. In general, Δn is set to fall within a range of0.04 to 0.28, the cell gap is set to fall within a range of 1 to 10 μm,and the product of Δn and d is set to fall within a range of 0.25 to0.55 μm.

In FIG. 14, the transparent layer 403 and 414 disposed closer to theliquid crystal cell of the upper and lower polarizing plates may be alsoused as protective films of the polarizers 401 and 416. Of course, filmsto protect the polarizers 401 and 416 may be interposed between thetransparent layer 403 and 414. Although protective films are typicallydisposed on both of surfaces of the polarizers formed of polarizers suchas polyvinylalcohol film or the like, an outer protective film is notshown in FIG. 14. In addition, the upper and lower polarizing plates maybe integrally stacked with the second optically anisotropic layers 405 band 412 b and with the first optically anisotropic layers 405 a and 412a, and the stacked structure thereof may be assembled into the liquidcrystal display. In this aspect, the transparent layers may be also usedas supports of the protective layers of the polarizers and the opticallyanisotropic layers. In the liquid crystal display of the invention, thesupport of the first optically anisotropic layer (or the secondoptically anisotropic layer if any) may be also used as a protectivefilm of one of the polarizers. That is, an integrated ellipticalpolarizing plate including the transparent protective film, thepolarizer, the transparent protective film (used as a transparent layerhaving particular optical characteristic and a transparent support ofthe optically anisotropic layer), and the optically anisotropic layer inorder may be used. Since this integrated elliptical polarizing plate hasthe optically anisotropic layer having an optical compensation function,when the integrated elliptical polarizing plate is used, it is possibleto compensate the liquid crystal display precisely with a simpleconfiguration.

Although the TN mode liquid crystal display is shown in FIG. 14, theliquid crystal display of the invention may be any of a VA mode, an IPSmode, an OCB mode and an ECB mode, in addition to the TN mode. Inaddition, when the liquid crystal display employs a multi domainstructure in which one pixel is divided into a plurality of regions,vertical and horizontal viewing angle characteristics are averaged,thereby improving display quality.

The liquid crystal display of the invention is not limited to theconfiguration shown in FIG. 14, but may include other members. Forexample, a color filter may be interposed between the liquid crystalcell and the polarizer. In addition, in case of a transmission typeliquid crystal display, a backlight unit having a light source such as acold cathode or hot cathode fluorescent tube, a light emitting diode, afield emission device, or an electroluminescence device may be disposedbehind the liquid crystal cell. In addition, the liquid crystal displayof the invention may be of a reflection type. In this case, only onepolarizing plate may be disposed at an observation side, and areflecting film is disposed behind the liquid crystal cell or at aninner side of the lower substrate of the liquid crystal cell. Of course,a front light unit using the light source may be provided at a liquidcrystal cell observation side. In addition, in order to maketransmission and reflection mode of the liquid crystal displaycompatible with each other, the liquid crystal display may be ofsemi-transmission type including a reflection part and a transmissionpart in one pixel of the display device.

In addition, in order to increase emission efficiency of the backlight,a prism-shaped or lens-shaped condensation type luminance enhancementsheet (film) is stacked, or a polarization reflection type luminanceenhancement sheet (film) to decrease light loss due to absorption by thepolarizing plate may be stacked between the backlight and the liquidcrystal cell. In addition, a diffusion sheet (film) to make lightemitted from the backlight uniform may be stacked, or a sheet (film)formed by printing a reflection and diffusion pattern to obtain auniform in-plane light distribution may be stacked.

The liquid crystal display of the invention includes image direct-viewtype, image projection type and light modulation type display devices.The invention is particularly effective for an active matrix liquidcrystal display using three or two terminal semiconductor devices suchas TFT or MIM. Of course, the invention is also effective for a passivematrix liquid crystal display represented by a STN type which is calleda time division driving.

According to still another aspect (V-1), the invention provides a liquidcrystal display comprising a pair of first and second substratesdisposed opposite to each other, at least one of which has a transparentelectrode; a liquid crystal layer interposed between the pair of firstand second substrates, wherein liquid crystal molecules are aligned insubstantial parallel to surfaces of the first and second oppositesubstrates under application of no voltage and a twist angle between thefirst and second opposite substrates is 45° or less; a pair of first andsecond polarizers having absorption axes perpendicular to each other,with the liquid crystal layer interposed between the pair of first andsecond polarizers; at least one first retardation layer interposedbetween the first polarizer and the liquid crystal layer and/or betweenthe second polarizer and the liquid crystal layer; and a secondretardation layer interposed between the first polarizer and the liquidcrystal layer and including at least one kind of compound having adiscotic structural unit, wherein the summation of in-plane retardationRe(550) of the at least one first retardation layer for a wavelength of550 nm and the summation of thickness direction retardation Rth(550) forthe same wavelength satisfy the following conditions.0 nm<Re(550)<70 nm0 nm<Rth(550)<330 nm.

According to still another aspect (V-2), the invention provides a liquidcrystal display comprising a pair of first and second substratesdisposed opposite to each other, at least one of which has a transparentelectrode; a liquid crystal layer interposed between the pair of firstand second substrates, wherein liquid crystal molecules are aligned insubstantial parallel to surfaces of the first and second oppositesubstrates under application of no voltage and a twist angle between thefirst and second opposite substrates is 45° or less; a pair of first andsecond polarizers having absorption axes perpendicular to each other,with the liquid crystal layer interposed between the pair of first andsecond polarizers; at least one first retardation layer interposedbetween the first polarizer and the liquid crystal layer and/or betweenthe second polarizer and the liquid crystal layer; and a pair of secondretardation layers interposed between the pair of first and secondpolarizers and the liquid crystal layer, respectively, and each secondretardation layer including at least one kind of compound having adiscotic structural unit, wherein the summation of in-plane retardationRe(550) of the at least one first retardation layer for a wavelength of550 nm and the summation of thickness direction retardation Rth(550) forthe same wavelength satisfy the following conditions.0 nm<Re(550)<70 nm0 nm<Rth(550)<200 nm.

According to the above preferred aspect of the invention, a viewingangle as well as display quality of a homogeneous ECB type liquidcrystal display can be significantly improved. That is, the inventioncan provide a liquid crystal display, particularly a homogeneous ECBtype liquid crystal display, with remarkable improvement of displayquality and a viewing angle over conventional liquid crystal displays,with no complicated structure and little change of conventionalstructures.

Hereinafter, a liquid crystal display according to this aspect will bedescribed in detail.

FIG. 25 is a schematic sectional view showing an exemplary configurationof a liquid crystal display according to a first aspect of theinvention. A liquid crystal display shown in FIG. 25 comprisestransparent substrates 510 and 512, a homogeneous ECB liquid crystallayer 514 interposed between the transparent substrates 510 and 512, andpolarizers 516 and 518 formed of polarizers having absorption axesarranged perpendicular to each other. A retardation plate (firstretardation layer) 522 is interposed between the liquid crystal layer514 and the polarizer 518, and an optical compensation film (secondretardation layer) 526 containing a compound of a discotic structuralunit is interposed between the retardation plate 522 and the transparentsubstrate 512.

An alignment film (not shown) and an electrode film (not shown) areformed at inner surfaces of the upper transparent substrate 510 and thelower transparent substrate 512. Liquid crystal molecules in thehomogeneous ECB liquid crystal layer 514 are aligned in substantialparallel to a substrate surface under application of no voltage, and atwist angle between the substrates depends on a direction of rubbingtreatment to which the alignment film is subjected. The direction ofrubbing treatment to which the alignment film formed at the innersurfaces of the substrates 510 and 512 is subjected is, preferably, 45°or less, more preferably, in substantial parallel (±10°). With thisrange, a substantial parallel alignment (having a twist angle of lessthan 45°) without a twist structure can be obtained. The electrode filmhas a function of applying a voltage to the liquid crystal molecules inthe liquid crystal layer 514. The electrode film is typicallytransparent and is made of for example, indium tin oxide (ITO). Liquidcrystals injected and sealed between the upper and lower substrates 510and 512 have positive dielectric anisotropy Δ∈ and, generally,refractive anisotropy of Δn=0.06˜0.1 (589 nm, 20° C.). The thickness dof the liquid crystal layer is 2.5˜5 μm. Here, the brightness of whiteimage display is varied depending on the product (Δn·d) of the thicknessd and the refractive index anisotropy Δn. The effect of the invention isremarkable in a range of 200 nm≦Δn·d≦400 nm. It is preferable that theproduct Δn·d is 260 nm˜320 nm.

The polarizers 516 and 518 have a perpendicular Nicol arrangement inwhich an intersection angle between absorption axes of the polarizers516 and 518 is about 90°. In addition, the absorption axis of thepolarizer 516 intersects an alignment direction of liquid crystalmolecules (generally, a rubbing direction of the alignment film formedat the inner surface of the transparent substrate 510) positioned nearthe transparent substrate 510 closer to the polarizer 516 by about 45°,and the absorption axis of the polarizer 518 intersects an alignmentdirection of liquid crystal molecules (generally, a rubbing direction ofthe alignment film formed at the inner surface of the transparentsubstrate 512) positioned near the transparent substrate 512 closer tothe polarizer 518 by about 45° (35 to 55°). Although the polarizers 516and 518 generally include, on their both surfaces, protective filmsformed of a celluloseacylate film to protect the polarizers, protectivefilms to protect outer surfaces of the polarizers are not shown in FIG.25.

The retardation plate 522 as the first retardation layer has an opticalcharacteristic satisfying the following relationship.0 nm<Re(550)<70 nm0 nm<Rth(550)<330 nm

In this aspect, when the retardation plate 522 having the opticalcharacteristic is assembled into the liquid crystal display, a viewingangle characteristic, particularly a vertical viewing anglecharacteristic, is improved. In this aspect, it is preferable that theretardation plate 522 satisfies a condition of Rth (550 nm)≧−200 nm. Inaddition, it is preferable that the retardation plate 522 satisfies acondition of 100 nm≦Rth(550)≦230 nm from a standpoint of easemanufacture or practical use.

In addition, in FIG. 25, a polarizer protective layer 523 has littleeffect on retardation of incident light, and is formed of, for example,a low retardation celluloseacylate film, which is disclosed inJP-A-2006-30937.

In the liquid crystal display shown in FIG. 25, the second retardationlayer 526 as the optical compensation layer containing a compound havinga discotic structural unit is interposed between the polarizer 518 andthe liquid crystal layer 514. When the second retardation layer 526 isplaced, transmittance in black image display can be further reduced,thereby displaying an image with a wider viewing angle and highercontrast. In an ECB mode liquid crystal cell, in general, retardationremains since rising of liquid crystal molecules located near the cellsubstrate is not sufficient under application of a voltage (in blackimage display). The second retardation layer 526 cancels the remainingretardation. Accordingly, for example, when a driving voltage isincreased to suppress the remaining retardation, the second retardationlayer may be removed or may be an expansible polymer film made of amaterial other than the compound having the discotic structural unit oran optical compensation film using alignment of bar-like liquid crystalmolecules as long as they have the same operation. In addition, when thesecond retardation layer to cancel the remaining retardation ismanufactured using alignment of a compound having a discotic structuralunit, it is preferable that an alignment control direction of moleculesof the compound having the discotic structural unit is in substantialparallel to an alignment direction of liquid crystal molecules at aboarder of the transparent substrate. In general, the alignment controldirection can be controlled by a rubbing treatment direction of analignment film used to manufacture an optical compensation film or thelike. The second retardation layer may be interposed between one of thepair of polarizers and the liquid crystal layer, as shown in FIG. 25(the optical compensation film 526 in FIG. 25), or may be interposedbetween both of the pair of polarizers and the liquid crystal layer,respectively, as shown in FIGS. 26 to 28 (the optical compensation films524 and 526 in FIGS. 26 to 28). In addition, the arrangement of thefirst and second retardation layers is not particularly limited. Forexample, the second and first retardation layers may be arranged inorder from a side closer to the liquid crystal layer, or the first andsecond retardation layers may be arranged in order from a side closer tothe liquid crystal layer.

In the liquid crystal display of the invention, since the firstretardation layer may be also used as a protective film or a transparentsupport of one of the polarizers, for example, an integrated polarizingplate including a protective film, a polarizer and the first retardationlayer (also used as a protective film or a transparent support) in ordermay be used. In addition, the first retardation layer may be not onlyused as a protective film or a transparent support of one of thepolarizers, but also used as a support of the second retardation layer.For example, an integrated polarizing plate including a protective film,a polarizer, the first retardation layer (also used as a polarizerprotective film or a support of the second retardation layer), and thesecond retardation in order may be used. These integrated polarizingplates not only have a polarizing function but also contribute toextension of a viewing angle and reduction of display spots. Inaddition, since these integrated polarizing plates have a retardationlayer having an optical compensation function, the liquid crystaldisplay can be optically compensated with a simple configuration. Whenthe latter integrated polarizing plate is assembled into the liquidcrystal display, it is preferable that a protective film, a polarizer,the first retardation layer (also used as a protective film or atransparent support, and a support of the second retardation layer), andthe second retardation are arranged in order from the outside of thedevice (a side far way from a liquid crystal cell). The liquid crystaldisplay shown in FIG. 25 may be manufactured by, for example, attachingthe latter integrated polarizing plate as a lower polarizing plate 518Ito a liquid crystal cell 514I).

FIGS. 26A and 26B show an example of a configuration of a liquid crystaldisplay according to a second aspect of the invention. In FIGS. 26A and26B, the same members as in FIG. 25 are denoted by the same referencenumerals, and detailed explanation thereof will be omitted. The liquidcrystal display shown in FIGS. 26A and 26B comprises transparentsubstrates 510 and 512, a homogeneous ECB liquid crystal layer 514interposed between the transparent substrates 510 and 512, andpolarizers 516 and 518 formed of polarizers having absorption axesarranged perpendicular to each other. In the liquid crystal displayshown in FIGS. 26A and 26B, a retardation plate (first retardationlayer) 522 is interposed between the liquid crystal layer 514 and thepolarizer 518, and in the liquid crystal display shown in FIG. 26A, aretardation plate (first retardation layer) 520 is interposed betweenthe liquid crystal layer 514 and the polarizer 516. In addition, in theliquid crystal display shown in FIGS. 26A and 26B, optical compensationfilms (second retardation layers) 524 and 526 containing a compound of adiscotic structural unit is interposed between the retardation plate 520and the transparent substrate 510 and between the retardation plate 522and the transparent substrate 512, respectively. The opticalcompensation films (second retardation layers) 524 and 526 containing acompound of a discotic structural unit have the same function as theoptical compensation film 526 shown in FIG. 25.

In the liquid crystal display shown in FIG. 26A, for the retardationplates 522 and 520 as the first retardation layer, the summation ofin-plane retardation Re(550) of a wavelength of 550 nm and the summationof thickness direction retardation Rth(550) of the same wavelengthsatisfy the following condition, and, in the liquid crystal displayshown in FIG. 26B, for the retardation plate 522 as the firstretardation layer, the in-plane retardation Re(550) of a wavelength of550 nm and the thickness direction retardation Rth(550) of the samewavelength satisfy the following condition.0 nm<Re(550)<70 nm0 nm<Rth(550)<330 nm

When the retardation plates 520 and 522 whose overall opticalcharacteristic satisfies the above relationship are assembled into inthe liquid crystal display shown in FIG. 26A, and when the retardationplate 522 whose optical characteristic satisfies the above relationshipis assembled into in the liquid crystal display shown in FIG. 26B, aviewing angle characteristic, particularly a vertical viewing anglecharacteristic, is improved. In this aspect, it is preferable that thesummation of the thickness direction retardation Rth(550) for thewavelength of 550 nm of at least one of the first retardation layerssatisfies the condition of 70 nm≦Rth(550)≦130 nm.

As described above, in the liquid crystal display shown in FIGS. 26A and26B, the support of the optical compensation film 524 or 526 containingthe compound having the discotic structural unit may be also used as thepolarizer protective layer 523 or the retardation plate 520 or 522. Inthis case, an integrated polarizing plate including the protective film,the polarizer, the support of the second retardation layer (also used asthe protective film of the polarizer or the first retardation layer),and the second retardation layer in order may be used as an upperpolarizing plate 516 or 516 b and a lower polarizing plate 518 a or 518b.

FIGS. 27C and 27D show another example of the liquid crystal display ofthe invention. In FIGS. 27C and 27D, the same members as in FIGS. 25 and26 are denoted by the same reference numerals, and detailed explanationthereof will be omitted. In the liquid crystal display shown in FIG.27C, the retardation plates 520 and 522 arranged at the outside of theliquid crystal cell 514 a in the liquid crystal display shown in FIG.26A are arranged as retardation layers 520′ and 522′ at an inner side ofa liquid crystal cell 514 c, and in the liquid crystal display shown inFIG. 27D, the retardation plate 522 arranged at the outside of theliquid crystal cell 514 b in the liquid crystal display shown in FIG.26B is arranged as a retardation layer 522′ at an inner side of a liquidcrystal cell 514 d. The liquid crystal displays shown in FIGS. 27C and27D have the same effect as the liquid crystal displays shown in FIGS.26A and 26B. In addition, in the liquid crystal displays shown in FIGS.27C and 27D, since the first retardation layer having the opticalcompensation function is disposed at an inner side of the substrate ofthe liquid crystal, that is, a position closer to the liquid crystallayer, the liquid crystal layer can be optically compensated moreprecisely, thereby obtaining better image display.

The liquid crystal cells 514 a and 514 c of the liquid crystal displaysshown in FIGS. 27C and 27D may be manufactured by preparing a cellsubstrate manufactured by forming the first retardation layer on asurface of a transparent substrate made of for example, glass, as one orboth of a pair of substrates, with the first retardation layer arrangedat inner sides of the substrates, and injecting and sealing liquidcrystal material between the substrates.

FIGS. 27C and 27D show still another example of the liquid crystaldisplay of the invention. In FIGS. 28E and 28F, the same members as inFIGS. 25 to 27 are denoted by the same reference numerals, and detailedexplanation thereof will be omitted. In the liquid crystal display shownin FIG. 28E, the retardation plates 524 and 526 that contain thecompound having the discotic structural unit and arranged at the outsideof the liquid crystal cell 514 c in the liquid crystal display shown inFIG. 27C are arranged as retardation layers 524″ and 526′ at an innerside of a liquid crystal cell 514 e, and in the liquid crystal displayshown in FIG. 28F, the retardation plates 524 and 526 that contain thecompound having the discotic structural unit and arranged at the outsideof the liquid crystal cell 514 d in the liquid crystal display shown inFIG. 27D is arranged as retardation layers 524′ and 526′ at an innerside of a liquid crystal cell 514 f. The liquid crystal displays shownin FIGS. 28E and 28F have the same effect as the liquid crystal displaysshown in FIGS. 27C and 27D. In addition, in the liquid crystal displaysshown in FIGS. 28E and 28F, since the second retardation layer thatcontributes to cancellation of the remaining retardation is disposed atan inner side of the substrate of the liquid crystal, that is, aposition closer to the liquid crystal layer, transmittance in blackimage display of the liquid crystal layer can be further reduced,thereby obtaining image display with higher contrast. In addition, aswill be described later, when the liquid crystal layer has two or morepicture regions and an optical compensation film containing a compoundhaving a discotic structural unit is arranged in the liquid crystallayer, since the optical compensation film can be partitionedcorresponding to the picture regions and an alignment direction ofdiscotic liquid crystal molecules can be optimized corresponding to thepicture regions for each of partitions, a liquid crystal display withhigher display quality can be realized.

The liquid crystal cell 514 e of the liquid crystal displays shown inFIG. 28E may be manufactured by preparing a cell substrate manufacturedby forming the second retardation layer containing the compound havingthe discotic structural unit and the first retardation layer on asurface of a transparent substrate made of, for example, glass, as apair of substrates, with the first and second retardation layersarranged at inner sides of the substrates, and injecting and sealingliquid crystal material between the substrates. In addition, the liquidcrystal cell 514 f of the liquid crystal displays shown in FIG. 28F maybe manufactured by preparing a cell substrate manufactured by formingthe second retardation layer containing the compound having the discoticstructural unit on a surface of a transparent substrate made of, forexample, glass, and a cell substrate manufactured by forming the secondretardation layer containing the compound having the discotic structuralunit and the first retardation layer on a surface of a transparentsubstrate made of, for example, glass, as a pair of substrates, with thefirst and second retardation layers arranged at inner sides of thesubstrates, and injecting and sealing liquid crystal material betweenthe substrates.

The liquid crystal display of the invention is not particularly limitedin its driving voltage, but may be driven within a general range ofdriving voltage of an ECB mode liquid crystal display. For example, theliquid crystal display of the invention may be driven in a normallywhite mode where a white image is displayed under application of novoltage, and a transmittance is decreased and a black image is displayedaccordingly under application of a high voltage. The black image isdisplayed when a Re value of an optical compensation film becomes equalto a retardation value of a liquid crystal layer under application of avoltage. With this configuration, it is advantageous that an image withhigh contrast can be obtained over a wide range, and there occurs nogray scale inversion in a halftone display region. In the invention,when an application voltage condition indicating transmittance lowerthan transmittance under application of no voltage is used as themaximum gray scale (white image display), a viewing angle can be furtherwidened.

When the liquid crystal display of the invention employs a multi domainstructure in which one pixel is divided into a plurality of regions, theviewing angle characteristic of luminance or color tone is furtherimproved. Specifically, by dividing one pixel into two or more(preferably, 4 or 8) regions having different initial alignment statesof liquid crystal molecules and averaging these regions, luminance andcolor tune depending on the viewing angle can be suppressed from beingbiased. In addition, the same effect is obtained even when one pixel isdivided into two or more different regions where the alignment directionof the liquid crystal molecules is continuously changed underapplication of a voltage.

A plurality of domains having different alignment directions of liquidcrystal molecules may be formed in one pixel by, for example, changingan electric field direction or biasing an electric field intensity usingslits provided in an electrode. A viewing angle that is substantiallyuniform in all directions may be obtained by increasing the number ofdomains, for example, by dividing one pixel into 4 or 8 or more domains.Particularly, it is preferable that one pixel is divided into 8 domainssince a polarizing plate absorption axis can be set at any angles.

Since liquid crystal molecules at borders of domains have poorresponsiveness and a white image display state remains in the normallywhite mode in case of ECB, a front contrast is deteriorated.Accordingly, it is preferable that a light shielding layer such as ablack matrix covers the borders of domains.

The liquid crystal display of the invention is not limited to theconfiguration shown in FIGS. 25 to 28, but may include other members.For example, a color filter may be interposed (an inner side or an outerside of the liquid crystal cell) between the liquid crystal cell and thepolarizer. In addition, a separate optical compensation film may beinterposed between the liquid crystal cell and the polarizing plate. Inaddition, in case of a transmission type liquid crystal display, abacklight unit having a light source such as a cold cathode or hotcathode fluorescent tube, a light emitting diode, a field emissiondevice, or an electroluminescence device may be disposed behind theliquid crystal cell. In addition, the liquid crystal display of theinvention may be of a reflection type. In this case, only one polarizingplate may be disposed at an observation side, and a reflecting film isdisposed behind the liquid crystal cell or at an inner side of the lowersubstrate of the liquid crystal cell. Of course, a front light unitusing the light source may be provided at a liquid crystal cellobservation side.

The liquid crystal display of the invention includes image direct-viewtype, image projection type and light modulation type display devices.The invention is particularly effective for an active matrix liquidcrystal display using three or two terminal semiconductor devices suchas TFT or MIM. Of course, the invention is also effective for a passivematrix liquid crystal display represented by a STN type which is calleda time division driving.

According to another preferred aspect (VI), the invention provides aliquid crystal display comprising a pair of opposite substrates, atleast one of which has an electrode; a liquid crystal layer includingliquid crystal molecules aligned by alignment axes of opposite surfacesof the pair of opposite substrates; a pair of polarizing plates eachhaving a polarizer and a protective film formed on at least one side ofthe polarizer, with the liquid crystal layer interposed between the pairof polarizing plates; and at least one optically anisotropic layeraligned by an alignment axis and including a liquid crystal compoundfixed with the alignment state between the liquid crystal layer and atleast one of the pair of polarizing plates, wherein an absorption of thepolarizer is in parallel or perpendicular to a horizontal direction of ascreen of the display device, at least one of the alignment axes of theopposite surfaces of the pair of opposite substrates intersects analignment control direction of the least one optically anisotropic layerby 10˜35°, and, assuming that in-plane retardation of the protectivefilm is Re (nm) and thickness direction retardation of the protectivefilm is Rth (nm), Re and Rth satisfy the following equation.Re+2×Rth≦280

In the liquid crystal display according to this aspect, by adjusting anarrangement angle relationship between the polarizing plate absorptionaxis, the alignment control direction of the liquid crystal substrate,and the alignment control direction of the optical compensation sheet,there can be provided a liquid crystal display, particularly a TN modeliquid crystal display, with high reliability and good display qualityin upper, lower, left and right inclined directions even under severeuse environments, with the same configuration as the conventional liquidcrystal display.

Hereinafter, the above aspect of the invention will be described indetail.

According to this aspect, the invention provides a liquid crystaldisplay comprising a pair of opposite substrates, at least one of whichhas an electrode, a liquid crystal layer containing liquid crystalmolecules controlled to be aligned by an alignment axis of each ofopposite planes of the pair of substrates, a pair of polarizing plateseach having a polarizer and a protective film formed on at least oneside of the polarizer, with the liquid crystal layer interposedtherebetween, and at least one optically anisotropic layer that isinterposed between the liquid crystal layer and at least one of the pairof polarizing plates and contains a liquid crystal compound controlledto be fixedly aligned by an alignment axis, wherein an absorption axisof the polarizer is in substantial parallel or perpendicular to themaximal contraction direction of the polarizing plate, that is, long andshort directions of an end portion of the polarizing plate (or ahorizontal direction of a screen of the display device). With thisconfiguration, light leakage out of circumferences of the polarizingplates is decreased even under severe use environments (high temperatureand high humidity), for example, even under use environments oftemperature of 40° C. and humidity of 90% or temperature of 65° C. andhumidity of 80%. In addition, a required wide viewing anglecharacteristic is satisfied by adjusting an arrangement anglerelationship between the alignment axis of the liquid crystal substrateand the alignment control direction of the optically anisotropic layer.

The prevent inventors have discovered that light leakage out ofcircumferences of polarizing plates in conventional TN mode liquidcrystal displays is caused by retardation Re and Rth generated inpolarizing plate protective films due to a photoelastic effect bycontraction of the polarizing plates. Based on this discover, thepresent inventor have also discovered that the light leakage can bedecreased by adjusting an arrangement angle relationship between thealignment axis of the liquid crystal substrate, the alignment controldirection of the optically anisotropic layer for optical compensation,and the absorption of the polarizing plates.

The polarizing plates are contracted under severe environments.Particularly, contraction in a direction in parallel to long and shortsides of a screen becomes maximal. When an elastic force such ascontraction or expansion is applied to a film used in the polarizingplates, retardation is changed. In a configuration where an absorptionaxis of the polarizing plate intersects a generation direction of theretardation by 45°, light transmission becomes maximal, which isobserved as light leakage. In the invention, it has been discovered thatlight leakage is particularly reduced in a TN mode liquid crystal layer.

In a conventional TN mode liquid crystal layer, an absorption plateabsorption axis intersects a horizontal direction of a screen, that is,a long side direction of an end portion of a polarizing plate by 45°.Since a contraction direction of the polarizing plate is in parallel tolong and short directions of the end portion of the polarizing plate,such a conventional arrangement gives the maximal light leakage.

Accordingly, in the invention, it has been discovered that light leakagecan be decreased in the TN mode by making the polarizing plateabsorption axis parallel or perpendicular to the horizontal direction ofthe screen, that is, the long side direction of the end portion of thepolarizing plate.

(The configuration where the polarizing plate absorption axis of theliquid crystal display is in parallel or perpendicular to the horizontaldirection of the screen, that is, the long side direction of the endportion of the polarizing plate, is hereinafter sometimes called “0°-90°attachment”).

The TN mode liquid crystal display employs a TFT driving in order todisplay a high quality image having high contrast high precision. Forthe TFT driving, gate wiring lines and signal (or source) wiring linesare arranged in horizontal and vertical directions of a screen. Since acontraction direction of a polarizing plate is in parallel orperpendicular to these wiring lines, even if a polarizing plateabsorption axis is arranged in parallel or perpendicular to these wiringlines, the absorption axis is arranged in substantial parallel orperpendicular to the maximal contraction direction of the polarizingplate, that is, long and short side directions of an end portion of thepolarizing plate, thereby decreasing light leakage.

In addition, the TN mode liquid crystal display, in order to obtain awide viewing angle characteristic, it is preferable that the absorptionaxis of at least one of the pair of polarizing plates intersects thealignment axis formed at a plane opposite to the liquid crystal cellsubstrate arranged at a side of at least one of the polarizing plates byabout 45°.

Light leakage out of circumferences of the polarizing plate can bedecreased by making the polarizing plate absorption axis parallel orperpendicular to the long side direction of the end portion of thepolarizing plate. At this time, by inclining an alignment controldirection of the TN mode liquid crystal display, that is, an alignmentaxis of a substrate of a liquid crystal cell, by 45° with respect to thehorizontal direction of the screen, a substantially bilateralsymmetrical viewing angle characteristic can be obtained.

In the conventional TN mode, the alignment control direction of theliquid crystal cell is inclined by 45° with respect to the horizontaldirection of the screen, and a vertical viewing angle characteristic isasymmetrical while the horizontal viewing angle characteristic issymmetrical. However, since the polarizing plate absorption axis and aretardation axis of a protective film of the polarizing plate are alsoinclined by 45° with respect to the horizontal direction of the screen,light is leaked out of the circumference of the polarizing plate undersevere use environments.

Next, an embodiment where the invention is applied to a TN mode liquidcrystal display will be described with reference to the drawings.

Prior to description of the invention, an operation of the conventionalliquid crystal display shown in FIG. 31 will be described by way ofexample of a general TN mode. Here, using nematic liquid crystals havingpositive dielectric anisotropy as field effect liquid crystals, a TFT(active) driving will be described by way of an example.

A liquid crystal cell 609 to 613 comprises an upper substrate 609, alower substrate 613, and a liquid crystal layer having liquid crystalmolecules 611 interposed between these substrates 609 and 613. Alignmentfilms (not shown) are formed on surfaces of the substrates 609 and 613contacting the liquid crystal molecules 611 (hereinafter, these surfacesare sometimes referred to as “inner surfaces”), and alignment of theliquid crystal molecules 611 under application of no voltage orapplication of a low voltage is controlled by a rubbing treatment towhich the alignment films are subjected. In addition, transparentelectrodes (not shown) that apply a voltage to the liquid crystal layerhaving the liquid crystal molecules 611 are formed on the inner surfacesof the substrates 609 and 613.

In the TN type liquid crystal display, under a non-driving state where adriving voltage is not applied to the electrodes, the liquid crystalmolecules 611 in the liquid crystal cell are aligned in substantialparallel to substrate planes and alignment direction is twisted by 90°between the upper and lower substrates. In case of a transmission typedisplay device, light emitted from a backlight unit has linearpolarization after passing through a lower polarizing plate. Thelinearly polarized light propagates along the twisted structure of theliquid crystal layer, rotates a polarizing plane by 90°, and then passesthrough the upper polarizing plate. Accordingly, the display devicedisplays a white image.

On the other hand, when an application voltage is increased, the liquidcrystal molecules get stand perpendicularly to the substrate planeswhile being untwisted. In the TN type liquid crystal display underapplication of an ideal high voltage, the liquid crystal molecules arenearly completely untwisted, and, accordingly, have a state of alignmentnearly perpendicular to the substrate planes. At this time, since thereis no twisted structure in the liquid crystal layer, the linearlypolarized light that passed through the lower polarizing platepropagates without rotating the polarizing plane and is perpendicularlyincident into an absorption axis of the upper polarizing plate.Accordingly, the light is shielded and the display device displays ablack image.

In this manner, the TN type liquid crystal display achieves a functionas a display device by shielding or transmitting the polarized light. Ingeneral, a contrast ratio (CR) as a numerical value to indicate displayquality is defined by a ratio of white display luminance to blackdisplay luminance. A higher CR value gives a higher quality displaydevice. In order to increase a contrast ratio, it is important tomaintain a polarization state in a liquid crystal display.

Hereinafter, an example of a configuration of the TN mode liquid crystalcell is described. A liquid crystal cell is manufactured by rubbing andaligning the liquid crystals having positive dielectric anisotropy,anisotropic refractive index, Δn=0.0854 (589 nm, 20° C.) and Δ∈=+8.5,and is disposed between the upper and lower substrates 609 and 613. Thealignment of the liquid crystal layer is controlled by the alignmentfilm and the rubbing treatment. A director, a so-called tilt angle,indicating the alignment direction of the liquid crystal molecules isset to falls within a range of, preferably, about 0.1° to 10°. In thisembodiment, the director is set to be 3°. The rubbing treatment isperformed in a direction perpendicular to the upper and lowersubstrates, and the size of the tilt angle can be controlled by rubbingstrength and number. The alignment films are formed by applying andfiring a polyimide film. The size of a twist angle of the liquid crystallayer is defined by an intersection angle in a rubbing direction betweenthe upper and lower substrates and a chiral agent added to liquidcrystal material. In this embodiment, a chiral agent having a pitch of60 μm or so is added so that the twist angle is about 90°. The thicknessd of the liquid crystal layer is set to be 5 μm.

In addition, liquid crystal material LC is not particularly limited aslong as it is nematic liquid crystal. As dielectric anisotropy Δ∈increases, the driving voltage can be further reduced. As refractiveindex anisotropy Δn decreases, the thickness (gap) of the liquid crystallayer can be further thickened, thereby shortening time taken to injectand seal liquid crystals and reducing unbalance of the gap. In addition,as Δn increases, a cell gap can be further decreased, thereby allowing ahigher speed response. In general, Δn is set to fall within a range of0.04 to 0.28, the cell gap is set to fall within a range of 1 to 10 μm,and the product of Δn and d is set to fall within a range of 0.25 to0.55 μm.

An absorption axis 604 of the upper polarizing plate and an absorptionaxis 619 of the lower polarizing plate are stacked substantiallyperpendicularly to each other, the absorption axis 604 of the upperpolarizing plate and the rubbing direction (alignment axis) 610 of theupper substrate 609 of the liquid crystal cell are stacked in parallelto each other, and the absorption axis 619 of the lower polarizing plateand the rubbing direction (alignment axis) 612 of the lower substrate613 of the liquid crystal cell are stacked in parallel to each other.Although the transparent electrodes (not shown) are formed at the innersides of the alignment films of the upper and lower substrates 609 and613, the liquid crystal molecules 611 in the liquid crystal cell arealigned in substantial parallel to the substrate planes under anon-driving state where the driving voltage is not applied to theelectrodes, and as a result, the polarized light that passes through theliquid crystal panel propagates along the twist structure of the liquidcrystal molecules 6 and rotates the polarizing plane by 90°. That is,the liquid crystal display realizes the white image display under thenon-driving state. On the other hand, the liquid crystal molecules arealigned in a direction inclined by an angle with respect to thesubstrate planes under a driving state, and the light that passedthrough the lower polarizing plate has no retardation in the liquidcrystal layer by optically anisotropic layers 614 and 607, passesthrough the liquid crystal layer 611 with its polarization stateunchanged, and then is shielded by a polarizer 603. In other words, theliquid crystal display realizes the ideal black image display under thedriving state.

Protective films 605 and 616 near the liquid crystal cell of the upperand lower polarizing plates may be also used as supports of theoptically anisotropic layers 607 and 614, and the upper and lowerpolarizing plates may be integrally stacked with the opticallyanisotropic layers 607 and 614, and the stacked structure thereof may beassembled into the liquid crystal display.

In the liquid crystal display of the invention, a transparent support ofan optical compensation sheet may be also used as a protective film ofone of the polarizers. That is, an integrated elliptical polarizingplate including the transparent protective film, the polarizer, thetransparent protective film (also used as the transparent support), andthe optically anisotropic layer in order may be used. Since thisintegrated elliptical polarizing plate has the optically anisotropiclayer having an optical compensation function, it is possible tocompensate the liquid crystal display precisely with a simpleconfiguration when the integrated elliptical polarizing plate is used.In the liquid crystal display, it is preferable that the transparentprotective film, the polarizer, the transparent support, and theoptically anisotropic layer are stacked in order from the outside of thedevice (side far away from the liquid crystal cell).

Although the TN mode liquid crystal display is shown in FIG. 31, theliquid crystal display of the invention may be any of a VA mode, an IPSmode, an OCB mode and an ECB mode, in addition to the TN mode. Inaddition, when the liquid crystal display employs a multi domainstructure in which one pixel is divided into a plurality of regions,vertical and horizontal viewing angle characteristics are averaged,thereby improving display quality.

The liquid crystal display of the invention is not limited to theconfiguration shown in FIG. 31, but may include other members. Forexample, a color filter may be interposed between the liquid crystalcell and the polarizer. In addition, in case of a transmission typeliquid crystal display, a backlight unit having a light source such as acold cathode or hot cathode fluorescent tube, a light emitting diode, afield emission device, or an electroluminescence device may be disposedbehind the liquid crystal cell. In addition, the liquid crystal displayof the invention may be of a reflection type. In this case, only onepolarizing plate may be disposed at an observation side, and areflecting film is disposed behind the liquid crystal cell or at aninner side of the lower substrate of the liquid crystal cell. Of course,a front light unit using the light source may be provided at a liquidcrystal cell observation side. In addition, in order to maketransmission and reflection mode of the liquid crystal displaycompatible with each other, the liquid crystal display may be ofsemi-transmission type including a reflection part and a transmissionpart in one pixel of the display device.

In addition, in order to increase emission efficiency of the backlight,a prism-shaped or lens-shaped condensation type luminance enhancementsheet (film) is stacked, or a polarization reflection type luminanceenhancement sheet (film) to decrease light loss due to absorption by thepolarizing plate may be stacked between the backlight and the liquidcrystal cell. In addition, a diffusion sheet (film) to make lightemitted from the backlight uniform may be stacked, or a sheet (film)formed by printing a reflection and diffusion pattern to obtain auniform in-plane light distribution may be stacked.

The liquid crystal display of the invention includes image direct-viewtype, image projection type and light modulation type display devices.The invention is particularly effective for an active matrix liquidcrystal display using three or two terminal semiconductor devices suchas TFT or MIM. Of course, the invention is also effective for a passivematrix liquid crystal display represented by a STN type which is calleda time division driving.

With the arrangement of the polarizing plate as described above, thelight leakage can be suppressed by employing the 0°-90° attachment.However, when the optically anisotropic layer of the liquid crystallayer is arranged in the same manner as in the conventional liquidcrystal display, there arises a problem of bilateral asymmetry that a CRvariation is different in left and right directions when an observingpolar angle is changed.

The present inventors have found a configuration of a liquid crystaldisplay to overcome the above problem.

That is, it has been found that this problem can be overcome if anintersection angle of an alignment control direction of an opticallyanisotropic layer and an alignment control direction of a liquid crystallayer falls within a range of 10 to 35°.

It is preferable that an optically anisotropic layer and an alignmentcontrol direction of a liquid crystal layer falls within a range of 15to 25°.

With this configuration, a CR viewing angle can be extended andbilateral asymmetry can be improved for the 0°-90° attachment.

FIG. 32 shows an example of a liquid crystal display according to anembodiment of the invention. This example is merely used to explain theeffect of the invention without any limitation.

In FIG. 32, absorption axes of polarizers have 90° (perpendicular) and0° (parallel) with respect to a horizontal direction of a screen.Specifically, in FIG. 32, an absorption axis 604 of an upper polarizer603 has 90° (perpendicular) and an absorption axis 619 of a lowerpolarizer 618 has 0° (parallel) with respect to a horizontal directionof a screen.

In addition, in this embodiment, the alignment control direction of theoptically anisotropic layer intersects the alignment control directionof the liquid crystal layer. That is, rubbing directions 608 and 615 foralignment of support sides of the optically anisotropic layers 607 and614 intersect rubbing directions 610 and 612 for liquid crystalalignment of upper and lower substrates of a liquid crystal layer 611.

With this configuration, circumferential light leakage can be reducedand bilateral asymmetry of a CR viewing angle can be improved for the0°-90° attachment.

FIGS. 33A to 33C shows alignment control directions of the liquidcrystal layer 611 and the upper and lower optically anisotropic layers607 and 614 when viewed from a display plane side.

The alignment control direction 608 of the upper optically anisotropiclayer 607 and the liquid crystal side upper alignment control direction610 are arranged as shown in FIG. 33A.

Similarly, the alignment control direction 615 of the lower opticallyanisotropic layer 614 and the liquid crystal side lower alignmentcontrol direction 612 are arranged as shown in FIG. 33B.

At this time, an intersection angle between the optically anisotropiclayer alignment control directions and the liquid layer alignmentcontrol directions is θ(°). In FIG. 33A, an intersection angle of thealignment control directions 608 and 610 or an intersection angle of thealignment control directions 615 and 612 is θ. θ is, preferably, 10 to35°, more preferably, 13 to 32°, particularly preferably, 15 to 30°.

In addition, FIG. 33C shows overlap of upper and lower sides of theliquid crystal layer. An intersection angle between the alignmentcontrol directions 608 and 615 of the pair of upper and lower opticallyanisotropic layers 607 and 614 is φ(°). φ is, preferably, 80 to 100°,more preferably, 85 to 95°, particularly preferably, about 90°.

Although the above configuration reduces the circumferential lightleakage and improves the bilateral asymmetry of the CR viewing angle, itis not sufficient for a CR viewing angle in all directions, particularlyan incline direction.

Accordingly, it has been assumed that a CR viewing angle in alldirections, particularly an inclined direction, is widened by adjustingin-plane retardation (Re(nm)) and thickness direction retardation(Rth(nm)) of polarizing plate protective films 601, 605, 616 and 620 tobe proper values.

As a result, it has proved that optimal values of Re and Rth can bederived from the following relationship.

Preferably, Re+2×Rth≦280,

more preferably, Re+Rth≦140, and

particularly preferably, 0≦Re≦50 or 50≦Rth≦80.

Next, members used in the liquid crystal display of the invention willbe described.

In the invention, an optically anisotropic layer containing a liquidcrystal compound with a fixed alignment state is used for opticalcompensation of a liquid crystal cell. In the invention, the opticallyanisotropic layer is formed on a support and is assembled as an opticalcompensation sheet into the liquid crystal display. Alternatively, anintegrated elliptical polarizing plate including the opticalcompensation sheet and a linear polarizer may be assembled into theliquid crystal display. An example of methods of manufacturing theoptical compensation sheet and the polarizing plate having theintersection angle set as described above may include a method ofadjusting an alignment control direction or an expansion direction of anoptical compensation sheet and a polarizing plate with respect to a rollconveyance direction, a method of preparing an optical compensationsheet and a polarizing plate in a roll-to-roll manner and punching theoptical compensation sheet and the polarizing plate at a preset angle,etc, without being limited thereto.

(Optical Compensation Sheet)

An example of the optical compensation sheet usable for the inventionincludes an optically transparent support and an optically anisotropiclayer formed of a liquid crystal compound on the support. When theoptical compensation sheet is used in the liquid crystal device, theliquid crystal cell can be optically compensated without deterioratingother characteristics.

Hereinafter, material used for various members usable for the liquidcrystal display of the invention and a method of manufacturing themembers will be described in detail.

(Polarizing Plate)

In the invention, a polarizing plate for a liquid crystal display mayincludes a first protective film, a polarizer, and a light diffusionlayer in order. The polarizer is obtained by dyeing a polyvinylalcoholfilm or the like with iodine and expanding it. The polarizing plate isobtained by stacking the protective layers on both sides of thepolarizer and forming the light diffusion layer or stacking a lightdiffusion film having a pre-formed light diffusion layer on at least oneof the protective films. The polarizing plate is arranged at an outerside of the liquid crystal cell. It is preferable that a pair ofpolarizing plates each having a polarizer and a pair of protective filmswith the polarizer interposed therebetween is arranged with a liquidcrystal cell interposed between the pair of polarizing plates.

(Protective Film)

The polarizing plate of the invention comprises a polarizer and a pairof protective films stacked on both sides of the polarizer. A protectivefilm is not particularly limited, but may include, for example,celluloseacetates such as celluloseacetate, celluloseacetatebutylate,cellulosepropionate and the like, polycarbonate, polyolefin,polystyrene, polyester, etc. Available polymers (norbornene polymers,ARTON available from JSR Corporation, ZEONOR available from ZEONCorporation, etc.) may be used for the protective film. The opticalcompensation film may be used as one of the pair of protective films. Inaddition, it is preferable that the protective films of the inventionare transparent protective films.

(Light Diffusion Layer)

The light diffusion layer is made of translucent particles andtranslucent resin. The light diffusion layer is preferably formed on aprotective film closest to an observer, but may be arranged on aprotective film at an outer side close to a light source. Of course, thelight diffusion layer may be arranged within the protective film (forexample, between the polarizer and the protective film), within anoptical compensation film (for example, between the optical compensationfilm and the protective film), or within the liquid crystal cell. Hazevalues and a scattering light profile are adjusted by the translucentparticles and the translucent resin. In the invention, it is preferableto use translucent particles having one or two or more kinds ofdiameters or materials.

(Translucent Particles)

It is preferable that a difference between a refractive index of thetranslucent particles and a refractive index of the translucent resinforming the overall light diffusion layer (an optical average refractiveindex when inorganic particles are added to the translucent resin toadjust a refractive index of the light diffusion layer) is 0.03 to 0.30.When the difference is 0.03 or more, a good light diffusion effect isobtained without having a too small refractive index difference. Whenthe difference is 0.30 or less, there occurs no problem such aswhitening of the light diffusion layer due to excessive increase oflight diffusion. The refractive index difference is preferably 0.06 to0.25, more preferably, 0.09 to 0.20.

(First Translucent Particles)

The diameter of translucent particles (first translucent particles) toimprove display quality (or a viewing angle characteristic) of theliquid crystal display of the invention is preferably 0.5 to 3.5 μm,more preferably 0.5 to 2.0 μm. When the diameter is 0.5 μm or more, ascattering effect is large, a viewing angle characteristic is improved,and brightness is little changed without increase of back scattering.When the diameter is 2.0 μm or less, there arises no problem such asinsufficient improvement of a viewing angle characteristic due to asmall scattering effect. The diameter is particularly preferably 0.6 to1.8 μm, most preferably 0.7 to 1.6 μm. An angle distribution of lightscattering can be obtained by adjusting the diameter properly.

In the light diffusion layer suitable for the invention, forcompatibility of the viewing angle characteristic with the whitening, itis particularly preferable to adjust haze values and a scattering lightprofile through proper combination of the refractive index differencebetween the translucent particles and the translucent resin forming theoverall light diffusion layer and the diameter of translucent particles.

A larger light diffusion effect of the light diffusion layer gives ahigher improved viewing angle characteristic. However, there is a needto increase transmittance as much as possible in order to maintain frontbrightness for display quality of the liquid crystal display.

(Second Translucent Particles)

In the invention, it is preferable that translucent particles (secondtranslucent particles) with no main purpose of diffusion effect arefurther added to the light diffusion layer. The second translucentparticles are used to form unevenness on a surface of the lightdiffusion layer to provide an image intrusion prevention function. Thediameter of the second translucent particles is preferably more than thediameter of the first translucent particles, more preferably 2.5 to 10.0μm. With this diameter, a proper surface scattering effect can beobtained. When the diameter is 2.5 μm or more, high film hardness ispreferably obtained since a layer thickness need not be large when adesired surface unevenness is formed on the light diffusion layer. Whenthe diameter is 10 μm or less, good particle precipitation stability ispreferably obtained since weight of particles is not too large. Thediameter of the second translucent particles is particularly preferably2.7 to 9 μm, most preferably 3 to 8 μm.

In order to achieve good display quality for the liquid crystal displayof the invention, it is important to prevent image intrusion of externallight. A smaller surface haze value gives a smaller discoloration byexternal light, thereby obtaining higher display quality. However, sincethe image intrusion becomes large if a surface haze value is too small,there is a need to provide low reflectivity by forming a low refractiveindex layer having a refractive index lower than the refractive index ofthe light diffusion layer on the outermost layer. In order to controlthe surface haze value, it is preferable that a proper unevenness isformed on a resin layer surface by means of the second translucentparticles, without being limited thereto.

It is preferable that a difference between the refractive index of thesecond translucent particles and the refractive index of the translucentresin forming the overall light diffusion layer is smaller than adifference between the refractive index of the first translucentparticles and the refractive index of the translucent resin.

Surface roughness Ra of the surface unevenness of the light diffusionlayer is preferably 0.5 μm or less, particularly preferably 0.3 μm orless, most preferably 0.2 μm or less. The surface roughness Ra (centerline average roughness) may be measured based on JIS-0601.

A haze value of the light diffusion layer, particularly an internalscattering haze (internal haze) that makes a significant contribution todiffusion of transmission light, has a closed interrelationship with aviewing angle characteristic improvement effect. A viewing anglecharacteristic is improved when light emitted from a backlight isdiffused in the light diffusion layer disposed at a surface of thepolarizing plate at a viewing side. However, if the light is excessivelydiffused, front luminance is decreased, and accordingly, in theinvention, there is a need to set the internal haze of the lightdiffusion layer to be 45% to 80%. The internal haze is more preferably45% to 70%, particularly preferably 45% to 60%. An example of methods ofincreasing the internal scattering haze may include a method ofincreasing particle concentration of translucent particles with thepurpose of providing diffusivity or increasing thickness of a coatedfilm, a method of making a refractive index difference between particlesand resin large, etc.

In the invention, in order to improve display quality (or viewing anglecharacteristic) of the liquid crystal display, it is particularlypreferable that scattering light intensity of an emission angle 30° withrespect to light intensity of an emission angle θ° of a scattering lightprofile of a goniophotometer falls within a particular range. Thescattering light intensity of an emission angle 30° with respect tolight intensity of an emission angle θ° of a scattering light profile ofa goniophotometer is preferably 0.05% or more from a standpoint of aviewing angle characteristic, and preferably 0.03% or less from astandpoint of front luminance. Accordingly, in the invention, thescattering light intensity of the light diffusion layer is preferably0.05 to 0.3%, more preferably 0.05 to 0.2%, particularly preferably 0.05to 0.15%. In the invention, it is particularly preferable that the lightdiffusion layer satisfies the preferred range of the scattering lightintensity and the preferred range of the internal haze simultaneously.

In the invention, from a standpoint of compatibility of reduction ofimage intrusion with discoloration, the haze due to the surfacescattering of the polarizing plate (surface haze) is preferably 0.1 to30%, more preferably 10% or less, particularly preferably 5% or less.With stress laid on preventing deterioration of contrast by externallight, the surface haze is preferably 4% or less, more preferably 2% orless. Since the image intrusion is increased as the surface haze isreduced, an average value of integral reflectivity for 5° incident lightin a wavelength range of 450 nm to 650 nm is set to be preferably 3.0%or less, more preferably 2.0% or less, most preferably 1.0% or less byproviding a low refractive index layer. In the invention, in order toimprove the display quality (viewing angle characteristic) of the liquidcrystal display, it is necessary to adjust the internal haze, preferablyadjust the internal scattering, more preferably set the surface hazeand/or the reflectivity to fall within a proper range simultaneously,thereby improving the contrast even in a bright place as the mostpreferred effect.

The translucent particles may be monodisperse organic particles orinorganic particles. As unbalance of the diameter of the translucentparticles becomes reduced, since unbalance of a scatteringcharacteristic becomes reduced it is easier to design a clouding value(haze). Plastic beads are suitable for the translucent particles. It isparticularly preferable that material used for the translucent particleshas high transparency and the above-mentioned refractive indexdifference from the translucent resin.

An example of organic particles may include polymethylmethacrylate beads(refractive index 1.49), acryl-styrene copolymer beads (refractive index1.54), melamine beads (refractive index 1.57), polycarbonate beads(refractive index 1.57), styrene beads (refractive index 1.60),cross-linking polystyrene beads (refractive, index 1.61), polyvinylchloride beads (refractive index 1.60),benzoguanaminemelamineformaldehyde beads (refractive index 1.68), etc.An example of inorganic particles may include silica beads (refractiveindex 1.44 to 1.46), alumina beads (refractive index 1.63).

The translucent particles are preferably 3 to 30 wt %, more preferably 5to 20 wt % for the translucent resin of 100 wt %. If the translucentparticles are less than 3 wt %, scattering ability is not sufficient. Ifthe translucent particles are more than 30 wt %, image quality is likelyto be deteriorated or surface turbid is apt to occur.

However, since the above translucent particles are apt to beprecipitated in the resin composition (translucent resin), an inorganicfiller such as silica may be added to the translucent particles toprevent the precipitation. In addition, as the addition amount of theinorganic filler is increased, transparency of a coated film isadversely affected although it is effective in preventing theprecipitation of the translucent particles. Accordingly, it ispreferable that an inorganic filler having the diameter of 0.5 μm orless is so less than 0.1 wt % for the translucent resin thattransparency of the coated film is not deteriorated.

(Translucent Resin)

An example of the translucent resin may include a resin curable by anultraviolet ray or an electron beam, for example, an ionizing radiationcuring resin, a mixture of an ionizing radiation curing resin with athermoplastic resin and a solvent, and a thermosetting resin. In orderto grant hardness to the light diffusion layer, it is preferable thatthe ionizing radiation curing resin is mainly used.

The thickness of the light diffusion layer may be typically 1.5 μm to 30μm, preferably 3 μm to 20 μm. In general, when the thickness of thelight diffusion layer is 1.5 μm or more, the hardness is sufficient.When the thickness of the light diffusion layer is 30 μm or less, thereoccurs no problem of curl or brittleness.

A refractive index of the translucent resin is preferably 1.46 to 2.00,more preferably 1.48 to 1.90, particularly preferably 1.50 to 1.80 if alow refractive index layer is further provided. The refractive index ofthe translucent resin is a light diffusion layer average value measuredwithout including translucent particles. If the refractive index of thetranslucent resin is not too small, anti-reflectivity is notdeteriorated. If the refractive index of the translucent resin is nottoo large, coloration of reflected light is not strengthened. From thispoint, the above range is preferable. The refractive index of the lightdiffusion layer is set to a desired value in consideration of theanti-reflectivity and the coloration of reflected light.

A resin used as the translucent resin is preferably a polymer havingsaturated hydrocarbon or polyether as a main chain, more preferably apolymer having the saturated hydrocarbon as the main chain. In addition,the translucent resin is preferably cross-linked. The polymer having thesaturated hydrocarbon as the main chain is preferably obtained bypolymerization of an ethylene unsaturated monomer. In order to obtain across-linking resin, it is preferable that a monomer having two or moreethylene unsaturated groups is used.

An example of monomers having two or more ethylene unsaturated groupsmay include ester of polyhydric alcohol and methacrylic acid {forexample, ethyleneglycoldimethacrylate, 1,4-cyclohexanediacrylate,pentaerythritoltetra(meth)acrylate, pentaerythritoltri(meth)acrylate,trimethylolpropanetri(meth)acrylate, trimethylolethanetri(meth)acrylate,dipentaerythritoltetra(meth)acrylate,dipentaerythritolpenta(meth)acrylate,dipentaerythritolhexa(meth)acrylate,dipentaerythritolhexa(meth)acrylate,1,3,5-cyclohexanetrioltrimethacrylate, polyurethanepolyacrylate,polyesterpolyacrylate, etc.}, derivatives of vinylbenzene (for example,1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethylester,1,4-divinylcyclohexanone, etc.), vinylsulfone (for example,divinylsulfone), acrylamide (for example, methylenebisaciylamide), andmethacrylamide. Among these, an acrylate or methacrylate monomer havingat least 3 functional groups or an acrylate monomer having at least 5functional groups is preferable from a standpoint of film hardness, thatis, scratch resistance. A mixture of dipentaerythritolpentaacrylate anddipentaerythritolhexaacrylate available is particularly preferably used.

The monomer having these ethylene unsaturated groups may be dissolved ina solvent, along with various polymerization initiators and additives,coated, dried, and then cured by polymerization by ionizing radiation orheat.

Instead of or in addition to the monomer having two or more ethyleneunsaturated groups, a cross-linking structure by reaction of across-linking group may be introduced into the translucent resin. Anexample of the cross-linking group may include an isocyanate group, anepoxy group, an aziridine group, an oxazoline group, an aldehyde group,a carbonyl group, a hydrazine group, a carboxyl group, a methylol group,and an active methylene group. Metal alkoxide such as vinyl sulfonicacid, acid anhydride, cyanoacrylate derivatives, melamine, ethericmethylol, ester, urethane, tetramethoxysilane and the like may be usedas a monomer to introduce the cross-linking structure. A functionalgroup showing cross-linkage as a result of decomposition reaction, suchas block isocyanate group, may be used. That is, in the invention, across-linking group may show a reaction as a result of decompositionalthough it can not show a reaction directly. A binder having thesecross-linking groups can form a cross-linking structure when beingapplied and heated.

It is preferable that the translucent resin contains a high refractiveindex monomer and/or high refractive index metal oxide ultrafineparticles in addition to the polymer.

An example of the high refractive index monomer may includebis(4-methacryloylthiophenyl)sulfide, vinylnaphthalene,vinylphenylsulfide, 4-methacryloxyphenyl-4′-methoxyphenylthioether, etc.

An example of the high refractive index metal oxide ultrafine particlesmay preferably include particles that are formed of at least oneselected from oxides of zirconium, titanium, aluminum, indium, zinc, tinand antimony and have a diameter of 100 nm or less, preferably 50 nm orless. The high refractive index metal oxide ultrafine particles arepreferably oxide ultrafine particles of at least one selected fromaluminum, zirconium, zinc, titanium, indium, and tin, for example, ZrO₂,TiO₂, Al₂O₃, In₂O₃, ZnO, SnO₂, Sb₂O₃, ITO. Among these metal oxides,ZrO₂ is particularly preferable.

The addition amount of the high refractive index monomer or the metaloxide ultrafine particles is preferably 10 to 90 wt %, more preferably20 to 80 wt % for the total weight of the translucent resin.

It is preferable that the light diffusion layer is applied on atransparent base film, which is also used as a protective film of apolarizer, preferably on a celluloseacetate film. A solvent of anapplication solution to form the light diffusion layer comprises atleast one kind of solvent to dissolve the transparent base film (forexample, a triacetyl cellulose film) and at least one kind of solventnot to dissolve the transparent base film in order to make excessivepenetration of diffusion layer components into the transparent base filmcompatible with close adhesion between the diffusion layer and thetransparent base film. It is more preferable that at least one kind ofsolvent to dissolve the transparent base film has a higher boiling pointthan at least one kind of solvent not to dissolve the transparent basefilm. A boiling point difference between a solvent having the highestboiling point to dissolve the transparent base film and a solvent havingthe highest boiling point not to dissolve the transparent base film isparticularly preferably 30° C. or more, most preferably more than 40° C.or more.

An example of the solvent to dissolve the transparent base film(preferably, triacetylcellulose) may include ethers having 3 to 12carbons, specifically, dibutylether, dimethoxymethane, dimethoxyethane,diethoxyethane, propyleneoxide, 1,4-dioxane, 1,3-dioxolane,1,3,5-trioxane, tetrahydrofuran, anisole, phenetole, etc.; ketoneshaving 3 to 12 carbons, specifically, acetone, methylethylketone,diethylketone, dipropylketone, diisobutylketone, cyclopentanone,cyclohexanone, methylcyclohexanone, etc.; esters having 3 to 12 carbons,specifically, formic acid ethyl, formic acid propyl, formic acidn-pentyl, methyl acetate, ethyl acetate, methyl propionate, ethylpropionate, n-pentyl acetate, γ-butyrolactone, etc.; an organic solventhaving two or more kinds of functional groups, specifically,2-methoxymethyl acetate, 2-ethoxymethyl acetate, 2-ethoxyethyl acetate,2-ethoxyethyl propionate, 2-methoxyethanol, 2-propoxyethanol),2-butoxyethanol, 1,2-diacetoxyacetone, acetylacetone, diacetonealcohol,acetic acid methyl, acetic acid ethyl, etc. These solvents may be usedsolely or in combination of two or more kinds. The ketone solvent ispreferably used as the solvent to dissolve the transparent base film.

An example of the solvent not to dissolve the transparent base film(preferably, tri-acetyl-cellulose may include methanol, ethanol,1-propanol, 2-propanol, 1-butanal, 2-butanol, t-butanol, 1-pentanol,2-methyl-2-butanol, cyclohexanol, isobutyl acetate,methylisobutylketone, 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone,3-pentanone, 3-heptanone, 4-heptanone, toluene, etc. These solvents maybe used solely or in combination of two or more kinds.

A weight ratio (A/B) of the gross weight of the solvent to dissolve thetransparent film (A) to the gross weight of the solvent not to dissolvethe transparent film (B) is preferably 5/95 to 50/50, more preferably10/90 to 40/60, particularly preferably 15/85 to 30/70.

The ionizing radiation curable resin composition may be cured by atypical method, for example, electron beam or ultraviolet ray radiation.

For example, in case of electron beam curing, electron beams havingenergy of 50 to 1000 KeV, preferably 100 to 300 KeV, which are emittedfrom various electron beam accelerators of Cockroft-Walton type, VandeGraaff type, resonance type, insulated core transformer type, lineartype, Dynamitrone type, high frequency type, etc., are used. In case ofultraviolet ray curing, ultraviolet rays emitted from light sources suchas an ultrahigh pressure mercury lamp, a high pressure mercury lamp, alow pressure mercury lamp, a carbon-arc, a xenon-arc, a metal halidelamp and so on are used.

(Photoinitiator)

An example of a photo-radical polymerization initiator may includeacetophenones, benzoins, benzophenones, phosphine oxides, ketals,anthraquinones, thioxanthones, azo compound, peroxides(JP-A-2001-139663, etc.), 2,3-dialkyldione compounds, disulfidecompounds, fluoroamine compounds, aromatic sulfoniums, lophine dimmers,onium salts, borate salts, active esters, active halogens, inorganiccomplexes, coumalins, etc.

An example of the acetophenones may include 2,2-dimethoxyacetophenone,2,2-diethoxyacetophenone, p-dimethylacetophenone,1-hydroxy-dimethylphenylketone,1-hydroxy-dimethyl-p-isopropylphenylketone,1-hydroxycyclohexylphenylketone,2-methyl-4-methylthio-2-morpholinopropiophenone,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone,4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, etc.

An example of active halogens may include compounds disclosed in “K.Wakabayashi et al, “Bull chem. Soc Japan”, Volume 42, p. 2924 (1969)”,U.S. Pat. No. 3,905,815, JP-A-5-27830, “M. P. Hutt, “Journal of Heterocyclic Chemistry”, Volume 1 (No. 3) (1970)”, particularly an oxazolecompound or a s-triazine compound substituted with a trihalomethylgroup, more preferably s-triazine derivatives in which at least onemono-, di-, or trihalogen substituted methyl group is combined to as-triazine ring.

An example of the s-triazine derivatives may include S-triazine oroxathiazole compounds, particularly,2-(p-methoxyphenyl)-4,6-bis(tricrolmethyl)-s-triazine,2-(p-styrylphenyl)-4,6-bis(tricrolmethyl)-s-triazine,2-(3-Br-4-di(ethylacetateester)amino)phenyl)-4,6-bis(tricrolmethyl)-s-triazine,2-trihalomethyl-5-(p-methoxyphenyl)-1,3,4-oxadiazole, etc.

Specifically, compounds disclosed in JP-A-58-15503 (p. 14 to 30),JP-A-55-77742 (p. 6 to 10), JP-A-60-27673 (Nos. 1 to 8 of p. 287),JP-A-60-239736 (Nos. 1 to 17 of p. 443 and 444), U.S. Pat. No. 4,701,399(Nos. 1 to 19), etc. are particularly preferable.

An example of the active halogens is as follows.

These initiators may be used solely or in combination.

Various examples of the initiators useful for the invention aredescribed in “The newest UV curing technology”, “Technology andinformation association Co., Ltd., p 159, 1991”, and “‘UV curing system’authored by K. Kato (published by General technology center, p 65-148,1989.”

An example of the photo-radical polymer initiator may include KAYACURE(DETX-S, BP-100, BDMK, CTX, BMS, 2-EAQ, ABQ, CPTX, EPD, ITX, QTX, BTC,MCA, etc.) which is available from Nippon Kayaku Co., Ltd., IRGACURE(651, 184, 500, 907, 369, 1173, 2959, 4265, 4263, etc.) which isavailable from Ciba Specialty Chemicals Co., Ltd., ESACURE (KIP100F,KB1, EB3, BP, X33, KT046, KT37, KIP150, TZT, etc.) which is availablefrom Sartomer Company Inc., and a combination thereof.

The photo-radical polymer initiator is used within a range of,preferably 0.1 to 15 wt %, more preferably 1 to 10 wt %, ofmultifunctional monomer of 100 wt %.

(Low Refractive Index Layer)

In the invention, although the object of the invention can be achievedby at least one light diffusion layer having the photo-radical polymerinitiator of the above-mentioned range, an anti-reflection function isobtained by forming a layer, which has a refractive layer lower than arefractive index of a layer adjacent to the outermost layer, on theoutermost layer. Accordingly, since the image intrusion of externallight can be suppressed and a high contrast can be obtained even in abright place, a image forming apparatus having higher image quality canbe obtained.

Next, material used for the low refractive index layer will bedescribed.

(Curable Composition)

The low refractive index layer of the invention is formed by applyingand curing a curable composition having a fluorine-containing compoundas a main component or a curable composition containing a monomer havinga plurality of linkable groups in a molecule and low refractive indexparticles and adjusting a refractive index to falls within a range of1.20 to 1.50, preferably a range of 1.25 to 1.45, more preferably arange of 1.30 to 1.40.

The curable composition may preferably include:

(1) composition containing a fluorine-containing polymer having across-linked or polymeric functional group,

(2) composition having a hydrolysis condensate of a fluorine-containingorganosilane compound as a main component, and

(3) composition containing a monomer having two or more ethyleneunsaturated groups and inorganic particles having a hollow structure,

With this curable composition, an optical film having good scratchresistance is obtained even when used as the outermost layer as comparedto a low refractive index layer using magnesium fluoride or calciumfluoride. A dynamic friction coefficient of a surface of the cured lowrefractive index layer is preferably 0.03 to 0.05, and a contact angleof the cured low refractive index layer with water is preferably 90 to120°.

(1) Composition Containing a Fluorine-Containing Polymer Having aCross-Linked or Polymeric Functional Group

An example of the fluorine-containing polymer having a cross-linked orpolymeric functional group may include a copolymer with a monomer havinga cross-linked or polymeric functional group. For example, afluorine-containing monomer may include fluoroolefins (for example,fluoroethylene, vinylidenefluoride, tetrafluoroethylene,hexafluoropropylene, hexafluoroethylene, hexafluoropropylene,perfluoro-2,2-dimethyl-1,3-dioxole, etc.), partially or completelyfluorinated alkylester derivatives of (meta)acryl acid (for example,Biscoat6FM (available from Osaka Organic Chemical Industry., Ltd.) orM-2020 (available from Daikin Industries., Ltd.), etc.), partially orcompletely fluorinated vinylethers, etc.

An example of the monomer to grant cross-linkage property to the lowrefractive index layer may include a (meth)acrylate monomer having across-linkable functional group in a molecule, such as glycidylmethacrylate, and a monomer having a cross-linkable or polymericfunctional group, which is made by composing a fluorine-containingcopolymer of a monomer having a functional group such as hydroxyl groupand modifying substituents of the fluorine-containing copolymer, etc.Specifically, the monomer may be a (meth)acrylate monomer having acarboxyl group, a hydroxyl group, an amino group, a sulfonic acid group,etc (for example, (meth)acrylic acid, methylol(meth)acrylate,hydroxyalkyl(meth)acrylate, arylacrylate, etc). The latter monomer isdisclosed in JP-A-10-25388 and JP-A-10-147739.

The fluorine-containing polymer may contain copolymerizable componentsfrom a standpoint of solubility, dispersibility, applicability,anti-smudge, antistatic property, etc. It is particularly preferablethat the fluorine-containing polymer contains a silicon component toprovide anti-smudge and lubrication property in its main chain or a sidechain.

An example of methods of partially introducing polysiloxane into themain chain of the fluorine-containing polymer may include a method ofusing a polymeric initiator such as azo group-containing polysiloxaneamide (for example, “VPS-0501” or “VPS-1001” available from WakoPurechemical Industries, Ltd.) disclosed in, for example, JP-A-6-93100.In addition, an example of methods of introducing polysiloxane into theside chain of the fluorine-containing polymer may include a method ofintroducing polysiloxane having a reactive group at its one end (forexample, SILAPLANE series available from CHISSO Corporation) bypolymeric reaction, as disclosed in “‘J. Appl. Polym. Sci.’, Volume2000, p. 78, 1955”, JP-A-56-28219, a method of polymerizing apolysiloxane-containing siliconmacromer, etc.

The above-mentioned fluorine-containing polymer may be also used alongwith a curing agent having a polymerizable unsaturated group, asdisclosed in JP-A-2000-17028. In addition, the fluorine-containingpolymer may be also used along with a compound having afluorine-containing multifunctional polymerizable unsaturated group, asdisclosed in JP-A-2002-145952. An example of the compound having themultifunctional polymerizable unsaturated group may include a monomerhaving two or more ethylene unsaturated groups, preferably a hydrolysiscondensate of organosilane, particularly preferably a hydrolysiscondensate of organosilane containing a (meta)acryloyl group disclosedin JP-A-2004-170901.

Among these compounds, particularly when a compound having apolymerizable unsaturated compound in a fluorine-containing polymer bodyis used, scratch resistance can be also improved.

If the fluorine-containing polymer does not have sufficient curabilitysolely, required curability can be provided by mixing a cross-linkablecompound into the fluorine-containing polymer. For example, if thefluorine-containing polymer body contains a hydroxyl group, it ispreferable that various amino compounds are used as curing agents. Anexample of amino compounds used as cross-linkable compounds may includecompounds containing one or both of a hydroxyalkyl amino group and analkoxyalkyl amino group in total of more than two, specifically, amelamine compound, a urea compound, a benzoguanamine compound, aglycoluril compound, etc. It is preferable that organic acid or its saltis used to cure these compounds.

Examples of these fluorine-containing polymers are disclosed inJP-A-2003-222702 and so on.

(2) Composition Having a Hydrolysis Condensate of a Fluorine-ContainingOrganosilane Compound as a Main Component

The composition having the hydrolysis condensate of thefluorine-containing organosilane compound as the main component is alsopreferable since it has a low refractive index and high hardness of asurface its coated film, it is preferable that a fluorinated alkyl groupis a compound containing hydrolysable silanol in its one end or bothends and a condensate of tetraalkoxysilane. Examples of this compositionare disclosed in JP-A-2002-265866 and JP-A-2002-317152.

(3) Composition Containing a Monomer Having Two or More EthyleneUnsaturated Groups and Inorganic Particles Having a Hollow Structure.

Another preferred aspect may include a low refractive index layer formedof low refractive particles and a binder. The low refractive indexparticles may be either organic or inorganic, and have preferablyhollows therein. An example of hollow low refractive index particles mayinclude silica particles disclosed in JP-A-2002-79616. A refractiveindex of the particles is preferably 1.15 to 1.40, more preferably 1.20to 1.30. An example of the binder may include a monomer having theabove-mentioned two or more ethylene unsaturated groups.

It is preferable that the above-mentioned polymeric initiator is addedto the low refractive index layer of the invention. If the lowrefractive index layer contains a radical polymeric compound, thepolymeric initiator may be 1 to 10 wt %, preferably 1 to 5% for thecompound.

(Inorganic Particles)

Inorganic particles may be added to the low refractive index layer ofthe invention. Particles having a diameter corresponding to 15% to 150%,preferably 30% to 100%, more preferably 45% to 60% of the thickness ofthe low refractive index layer can be used to provide scratch resistanceto the low refractive index layer.

(Other Additives)

Known polysiloxane or fluorine anti-smudge agents, lubricant and so onmay be properly added to the low refractive index layer of the inventionto provide properties such as anti-smudge, waterproofing, chemicalresistance, lubricability and the like to the low refractive indexlayer.

In the invention, a film having the light diffusion layer has verticalseparation static charge of, preferably −200 pc/cm² to +200 pc/cm², morepreferably −100 pc/cm² to +100 pc/cm², particularly preferably −50pc/cm² to +50 pc/cm², most preferably 0 pc/cm², measured for eithertriacetylcellulose (TAC) or polyethyleneterephthalate (PET) under anormal temperature and normal humidity condition. Here, pc is 10⁻¹²coulomb. More specifically, vertical separation static charge measuredunder a normal temperature and 10% RH condition is preferably −200pc/cm² to +200 pc/cm², more preferably −50 pc/cm² to +50 pc/cm², mostpreferably 0 pc/cm².

A method of measuring the vertical separation static charge is asfollows.

A sample to be measured is left alone for more than 2 hours under ameasurement temperature and humidity. A measuring apparatus comprises amount on which the sample to be measured is placed, a head that holds acounterpart film and is repeatedly compressed/separated to/from thesample, and an electrometer connected to the head for measuring staticcharge. The film that is to be measured and has anti-glare andanti-reflection property is placed on the mount, and then TAC or PET isplaced on the head. Electricity is removed from a portion of the sampleto be measured, and the head is repeatedly compressed/separated to/fromthe sample. Values of charge for first and fifth separations are readand averaged. Thereafter, this process is repeated for three differentsamples. An average of all values of charge obtained in all of themeasured samples is assumed to be vertical separation static charge.

A surface resistance value of the film having the light diffusion layerof the invention is preferably 1×10⁷Ω/□ to 1×10¹⁵Ω/□, more preferably1×10⁷Ω/□ to 1×10¹⁴Ω/□, most preferably 1×10⁷Ω/□ to 1×10¹³Ω/□.

A method of measuring the surface resistance value is a circle electrodemethod disclosed in JIS. That is, a surface resistance value (SR) isobtained from a current value read when one minute elapses afterapplication of a voltage.

It is preferable that an antistatic prevention layer is provided todecrease the surface resistance value. Preferred layer structures are asfollows. In the following structures, a base film is also used as asecond protective film.

-   -   base film/light diffusion layer/antistatic prevention layer/low        refractive index layer    -   base film/antistatic prevention layer/light diffusion layer/low        refractive index layer    -   base film/light diffusion layer(antistatic prevention layer)/low        refractive index layer        -   base film/light diffusion layer/medium refractive index            layer(antistatic prevention layer)/high refractive index            layer/low refractive index layer        -   base film/light diffusion layer(antistatic prevention            layer)/medium refractive index layer/high refractive index            layer/low refractive index layer        -   base film/antistatic prevention layer/light diffusion            layer/medium refractive index layer/high refractive index            layer/low refractive index layer        -   base film/light diffusion layer/medium refractive index            layer/high refractive index layer(antistatic prevention            layer)/low refractive index layer

The above structures are not limitative. For example, the low refractiveindex layer may be removed from the above structures. It is preferablethat the antistatic prevention layer is a layer containing conductivepolymer particles or metal oxide particles (for example, ATO, ITO,etc.). The antistatic prevention layer may be provided by application oratmosphere plasma treatment or the like. An anti-smudge layer may beformed on the uppermost layers of the above structures.

In order to increase film hardness (provide scratch resistance), it ispreferable that at least one hard coat layer (without or with lightdiffusion property) is provided as a separate layer in addition tothickening the light diffusion layer having the hard coat property. Forthis hard coat layer, preferred layer structures are as follows. In thefollowing structures, a base film is also used as a second protectivefilm.

-   -   base film/hard coat layer/light diffusion layer/low refractive        index layer    -   base film/light diffusion layer/hard coat layer/low refractive        index layer

The above structures are not limitative. For example, the low refractiveindex layer may be removed from the above structures. In addition, it isalso preferable that the antistatic prevention layer is added to theabove structures.

In the invention, an average value of integral reflectivity of the filmhaving the light diffusion layer for 5° incident light in a wavelengthrange of 450 nm to 650 nm is preferably 3.0% or less, more preferably2.0% or less, most preferably 1.0% or less.

(Transparent Base Film)

A translucent resin film, a translucent resin plate, a translucent resinsheet or the like may be used as a material of a transparent base film.A transparent glass base material may be used instead of the transparentbase film. An example of the translucent resin film may include atriacetylcellulose (TAC) film (refractive index 1.48), adiacetylenecellulose film, an acetatebutyratecellulose film, apolyethyleneterephthalate (PET) film, a polyethersulfone film, apolyacryl resin film, a polyurethane resin film, a polyester film, apolycarbonate film, a polysulfone film, a polyester film, apolymethylpentene film, a polyetherketone film, a (meth)acrylonitrilefilm, etc. The thickness of the transparent base film is typically inthe range of 25 to 200 μm, preferably in the range of 30 to 100 μm, morepreferably in the range of 40 to 80 μm. Since the transparent base filmis also used for the outermost of the polarizing plate, it is preferablethat a celluloseacetate film generally used as a protective film of thepolarizing plate is used as the transparent base film. A transparentbase film of the light diffusion layer is preferably a celluloseacetatefilm having high transparency and a smooth surface.

(Celluloseacetate Film)

In the invention, it is particularly preferable that celluloseacetatehaving acidity of 59.0 to 61.5% is used for the transparent base film.The acidity means the quantity of combined acetic acid per celluloseunit weight. The acidity is obtained by measuring and calculatingacetylation in ASTM: D-817-91 (test method for celluloseester and thelike). Viscosity-average degree of polymerization (DP) of celluloseesteris preferably 250 or more, more preferably 290 or more.

In addition, it is preferable that cellulosacetate used in the inventionhas a narrow molecule weight distribution of Mw/Mn (Mw is aweight-average molecule weight and Mn is a number-average moleculeweight) by a gel permeation chromatography (GPC). Specifically, a valueof Mw/Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, mostpreferably 1.4 to 1.6.

In general, in celluloseacylate, the degree of substitution of second,third and sixth-position hydroxyl groups of the cellulose unit is notevenly distributed by ⅓, but the degree of substitution ofsixth-position hydroxyl group tends to become small. In the invention,it is preferable that the degree of substitution of sixth-positionhydroxyl group of the cellulose unit of celluloseacylate is larger thanthose of second and third-position hydroxyl groups. For the total degreeof substitution, the second-position hydroxyl group is substituted withan acyl group by, preferably 32% or more, more preferably 33% or more,particularly preferably 34% or more. In addition, it is preferable thatthe degree of substitution of sixth-position hydroxyl group of thecellulose unit is 0.88 or more. The sixth-position hydroxyl group of thecellulose unit may be substituted with a propionyl group, a butyroylgroup, a valeroyl group, a benzoyl group, an acryloyl group, etc, whichare an acyl group having three or more carbons, in addition to an acetylgroup. The degree of substitution at each of the positions can beobtained by NMR. In the invention, an example of celluloseacylate mayinclude celluloseacetate obtained by the method disclosed in JP-A-1-5851(“Example 1” (Synthesis example 1) of paragraphs “0043” to “0044”,(Synthesis example 2) of paragraphs “0048” to “0049”, and (Synthesisexample 3) of paragraphs “0051” to “0052”).

(Organic Solvent Used in Solvent Cast Method)

It is preferable that the celluloseacetate film is manufactured by asolvent cast method. In the solvent cast method, the film ismanufactured by using a solution (dope) in which celluloseacetate isdissolved in an organic solvent. It is preferable that the organicsolvent contains a solvent selected from ether having 3 to 12 carbonatoms, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbonatoms, and halogenated hydrocarbon having 1 to 6 carbon atoms. Ether,ketone and ester may have a ring-shape structure. Compounds having twoor more functional groups (that is, —O—, —CO— and —COO—) of ether,ketone and ester may be used as the organic solvent. The organic solventmay have other functional groups such as an alcoholic hydroxyl group.The number of carbon atoms in the organic solvent having two or morekinds of functional groups may fall within a specified range of acompound having several carbon atoms.

An example of ethers having 3 to 12 carbon atoms may includediisopropylether, dimethoxymethane, dimethoxyethane, 1,4-dioxane,1,3-dioxolane, tetrahydrofuran, anisole and phenetole. An example ofketones having 3 to 12 carbon atoms may include acetone,methylethylketone, diethyl ketone, diisobutylketone, cyclohexanone andmethylcyclohexanone. An example of esters having 3 to 12 carbon atomsmay include ethylformate, propylformate, pentylformate, methylacetate;ethylacetate and pentylacetate.

An example of the organic solvent having two or more kinds of functionalgroups may include 2-ethoxyethylacetate, 2-methoxyethanol and2-buthoxyethanol. The number of carbon atoms of halogenated hydrocarbonis preferably 1 or 2, more preferably 1. It is preferable that halogenof halogenated hydrocarbon is chlorine. A ratio of substitution ofhydrogen atoms of halogenated hydrocarbon with halogen is preferably 25to 75 mol %, more preferably 30 to 70 mol %, particularly preferably 35to 65 mol %, most preferably 40 to 60 mol %. Methylenechloride istypical halogenated hydrocarbon. A mixture of two or more kinds oforganic solvents may be used.

(Plasticizer)

A plasticizer may be added to the celluloseacetate film in order toimprove mechanical properties or increase a drying speed. Phosphateester or carboxylic acid ester is used as the plasticizer. An example ofphosphate ester may include triphenyl phosphate (TPP) and tricresylphosphate (TCP). A typical example of carboxylic acid ester may includephthalate ester and citric acid ester. An example of phthalate ester mayinclude dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutylphthalate (DBP), dioctylphthalate (DOP), diphenyl phthalate (DPP) anddi-ethylhexyl phthalate (DEHP). An example of citric acid ester mayinclude O-acetyl citrate triethyl (OACTE) and O-acetyl citrate tributyl(OACTB). In addition, an example of carboxylic acid ester may includeoleic acid butyl, ricinoleic acid methylacetyl, sebacic acid dibutyl,various trimellitic acid esters. Phthalate ester plasticizers (DMP, DEP,DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularlypreferable.

The addition amount of plasticizer is preferably 0.1 to 25 wt %, morepreferably 1 to 20 wt %, most preferably 3 to 15 wt % of quantity ofcelluloseester.

A deterioration preventive agent (for example, an antioxidant, aperoxide decomposer, a radical inhibitor, metal deactivator, an acidcapture agent, amine, etc.) may be added to the celluloseacetate film.Examples of the deterioration preventive agent are disclosed in JP-ANos. 3-199201, 5-1907073, 5-194789, 5-271471, and 6-107854. The additionamount of deterioration preventive agent is preferably 0.01 to 1 wt %,more preferably 0.01 to 0.2 wt % of a solution (dope). When the additionamount of deterioration preventive agent is more than 0.01 wt %, a goodeffect of deterioration preventive agent is obtained. When the additionamount of deterioration preventive agent is less than 1 wt %, thedeterioration preventive agent will not be bled (permeated) out of afilm surface. An example of deterioration preventive agent may include,particularly preferably a butylated hydroxytoluene (BHT) andtribenzylamine (TBA).

(Surface Treatment of Celluloseacetate Film)

It is preferable that the celluloseacetate film is subjected to asurface treatment. An example of the surface treatment may include acorona discharging treatment, a glow discharging treatment, a flamingtreatment, an acid treatment, an alkali treatment and an ultraviolettreatment. In addition, it is also preferable to provide a base layer,as disclosed in JP-A-7-333433. In these treatments, from a standpoint offlatness of the film, it is preferable that the temperature of thecelluloseacetate film is less than Tg, specifically 150°. When thecelluloseacetate film is used as a transparent film of a polarizingplate, from a standpoint of adhesion with the polarizing plate, it isparticularly preferable that celluloseacetate is subjected to an acid oralkali treatment, that is, a saponification treatment. Surface energy ofthe obtained celluloseacetate film is preferably 55 mN/m or more, morepreferably 60 mN/m to 75 mN/m. In addition, in order to coat a layer(film) on the celluloseacetate film uniformly, it is also preferablethat the celluloseacetate film is subjected to a heat treatment toenhance flatness of the celluloseacetate film.

(Saponification Treatment)

When the polarizing plate of the invention is manufactured, it ispreferable to hydrophilize an adhesion surface between a protective filmand a polarizer to enhance adhesion at the adhesion surface.

a. Method to Digest Film into Alkali Solution

This method refers to a method in which a film is digested into analkali solution under proper conditions and all planes havingresponsiveness with alkali of the entire surface of the film aresubjected to the saponification treatment. This method is preferablefrom a standpoint of costs since it does not require special equipments.It is preferable that the alkali solution is a sodium hydroxide aqueoussolution. The concentration of the alkali solution is preferably 0.5 to3 mol/L, particularly preferably 1 to 2 mol/L. The temperature of thealkali solution is preferably 30 to 75° C., particularly preferably 40to 60° C. It is preferable that combination of these saponificationconditions is combination of relatively moderate conditions. Thecombination of these saponification conditions may be set depending onmaterial or configuration of the film or a target contacting portion.After the film is digested in the alkali solution, it is preferable toneutralize an alkali component by sufficiently washing the film ordigesting the film into a dilute acid solution so that the alkalicomponent does not remain in the film.

A surface opposite to a surface of an application layer is hydrophilizedby the saponification treatment. The protective film of the polarizingplate is obtained by bonding a hydrophilized surface of a transparentsupport to the polarizer. The hydrophilized surface is effective inenhancing adhesion with an adhesion layer having polyvinylalcohol as amain component.

The saponification treatment is preferable from a standpoint of adhesionwith the polarizing plate as a contact angle with water of the surfaceof the transparent support opposite to an application layer side becomessmall. However, in the digest method, since the surface and the innerside of the application layer are damaged, it is important to apply therequired minimal reaction conditions. When the contact angle with waterof the surface of the transparent support opposite to the applicationlayer side is used as an indicator of damage to each layer by alkali,particularly if the transparent support is made of triacetylcellulose,the contact angle is preferably 10° to 50°, more preferably 30° to 50°,particularly preferably 40° to 50°. When the contact angle is 50° orless, the adhesion with the polarizer has no problem. When the contactangle is 10° or more, physical strength of the film keeps constantwithout significant increase of damage to the film.

b. Method to Apply Alkali Solution

For the purpose of avoiding the damage to the film in theabove-described digest method, an alkali solution application method inwhich an alkali solution is applied only a surface opposite to a surfaceof the application layer under proper conditions and then the oppositesurface is heated, washed and dried is preferably used. In this case,the application means contact of alkali solution with only a surfacethat is subjected to the saponification treatment by means ofapplication, spray, contact with a belt containing a solution, etc. Thisapplication method requires separate equipments and processes to applythe alkali solution. Accordingly, the above-described digest method (a)is an advantage over this application method from a standpoint of cost.However, the application method has an advantage from a standpoint ofsaponification treatment in that a layer made of a material sensitive tothe alkali solution can be used in the opposite surface since the alkalisolution contacts only the surface that is subjected to thesaponification treatment. For example, it is not preferable that adeposition film made of aluminum or the like or a sol-gel film is usedin the digest method since the film is apt to be corroded, dissolved,peeled out, etc. by the alkali solution However, this film can be usedin the application method with no problem since the film does notcontact the alkali solution.

Since the saponification treatment of either the digest method (a) orthe application method (b) can be performed after forming each layer byunrolling the layer from a roll-shaped base film, the saponificationtreatment may be performed in a series of operations after manufacturingthe film. Similarly, by continuously performing a process of laminatingthe layer with an unrolled polarizer, a polarizing plate can be moreeffectively manufactured as compared to when the lamination process isseparately performed.

c. Method to Protect Application Layer with Laminate Film andSaponificating the Application Layer

Similarly to the application method (b), if an application layer hasinsufficient resistance to an alkali solution, the application layer isformed up to a final layer, a laminate film is laminated on a surface atwhich the final layer is formed, the final layer is digested into thealkali solution to hydrophilize only a triacetylcellulose side oppositeto the surface at which the final layer is formed, and then the laminatefilm is peeled out. In this method (c), a hydrophilic process requiredfor a polarizing plate protective film can be performed for the sideopposite to the surface at which the final layer of thetriacetylcellulose film is formed. In comparison to the applicationmethod (b), this method (c) does not require a special apparatus forapplying an alkali solution although the laminate film comes in disuse.

d. Method to Digest Application Layer into Alkali Solution after Formingthe Application Layer Up to Intermediate Layer

If an upper layer has insufficient resistance to an alkali solutionwhile a lower layer has sufficient resistance to the alkali solution,the lower layer is digested in the alkali solution to hydrophilize bothsides of the lower layer, and then the upper layer is formed on thelower layer. In case of a film having a hard coat layer and a lowrefractive index layer of a fluorine-containing sol-gel film, thismethod (d) has an advantage of enhancement of interlayer adhesionbetween the hard coat layer and the low refractive index layer if thefilm has a hydrophilic group, although a manufacturing process becomessome complicated.

e. Method to Form Application Layer on Triacetylcellulose Film ofSaponification Agent in Advance

A triacetylcellulose film may be saponificated in advance by digestingthe film in an alkali solution, and an application layer may be formedon one side of the film directly or via a different layer. When thetriacetylcellulose film is digested into the alkali solution andaccordingly is saponificated, an interlayer adhesion with atriacetylcellulose plane hydrophilized by the saponification may bedeteriorated. In this case, such deterioration of the interlayeradhesion can be avoided when the application layer is formed afterremoving a hydrophilic plane by performing a corona dischargingtreatment, a glow discharging treatment or the like for only a surfaceforming the application layer after saponification. In addition, if theapplication has a hydrophilic group, the interlayer adhesion may begood.

(Manufacture of Polarizing Plate)

In the invention, a polarizing plate for the liquid crystal display ofthe invention can be manufactured by arranging transparent base films,such as triacetylcellulose films, as protective films on both sides of apolarizer and then forming a light diffusion layer on at least oneprotective film or stacking a light diffusion film having a formed lightdiffusion layer on the polarizer. The transparent base film used may bean available triacetylcellulose film. But, as the transparent base film,it is preferable to use a triacetylcellulose film that is manufacturedusing the above-described solution film forming methods and is expandedin a width direction in a roll film shape with an expansionmagnification of 10 to 100%. In addition, in the polarizing plate of theinvention, an optical compensation film having an optically anisotropiclayer containing a liquid crystal compound may be stacked on oneprotective film, or this protective film may be also used as an opticalcompensation film.

An example of the polarizer may include an iodine polarizer, a dyepolarizer using a dichroic dye and a polyene polarizer. In general, theiodine polarizer and the dye polarizer are manufactured using apolyvinylalcohol film.

Moisture permeability of a protective film is important for productivityof the polarizing plate. The polarizer and the protective film arelaminated by a water-base adhesive, and this adhesive solvent isdiffused into the protective film and is dried. A higher moisturepermeability of the protective film gives a faster drying of theadhesive solution, thereby improving productivity. However, if themoisture permeability is too high, moisture permeates into the polarizerunder high humidity use environments of the liquid crystal display,thereby deteriorating polarizability. The moisture permeability of theprotective film depends on the kind of transparent base film; and itsthickness (thickness including a liquid crystal compound if theprotective film is an optical compensation film), free volume,hydrophilic and hydrophobic properties, etc.

In the polarizing plate of the invention, the moisture permeability ofthe protective film is preferably 100 to 1000 g/m²·24 hrs, morepreferably 300 to 700 g/m²·24 hrs.

The thickness of the transparent base film may be adjusted by lip flow,line speed, expansion, compression and the like when the film ismanufactured. Since the moisture permeability is varied depending on amain material used, it is possible to set the moisture permeability tofall within a preferred range by thickness adjustment. The free volumeof the transparent base film may be adjusted by dry temperature andtime. In this case, since the moisture permeability is also varieddepending on a main material used, it is possible to set the moisturepermeability to fall within a preferred range by free volume adjustment.The hydrophilic and hydrophobic properties of the transparent base filmmay be adjusted by additives. The moisture permeability is increased byadding a hydrophilic additive to the free volume, while the moisturepermeability is decreased by adding a hydrophobic additive to the freevolume. By controlling the moisture permeability independently, it ispossible to manufacture the polarizing plate having the opticalcompensation performance at low costs and with high productivity.

A retardation axis of a transparent base film or a triacetylcellulosefilm of an optical film and a transmission axis of a polarizer may bearranged in substantial parallel to each other.

An example of the polarizer may include a known polarizer, a polarizercut from a long polarizer whose absorption axis is neither parallel norperpendicular in a longitudinal direction, etc.

Typically, it is preferable that the protective film is continuouslylaminated on a long polarizer that is supplied in the form of a roll,with their longitudinal directions coincident with each other. Here, analignment axis (retardation axis) of the protective film may be in anydirection. For the sake of operational convenience, it is preferablethat the alignment of the protective film is either parallel orperpendicular in the longitudinal direction.

When the protective film and the polarizer are laminated each other,although the retardation axis (alignment axis) of at least oneprotective film (a protective film arranged at a side closer to a liquidcrystal cell when the protective film is mounted in the liquid crystaldisplay) may intersect the absorption axis (expansion axis) of thepolarizer, mechanical stability of the polarizing plate can be improvedto prevent dimensional change and curl of the polarizing plate when theretardation axis of the protective film is in parallel to the absorptionaxis of the polarizer. The same effect is obtained if at least two axesof three films including the polarizer and the pair of protective filmsare in substantial parallel to each other, if the retardation axis ofone protective film is in substantial parallel to the absorption axis ofthe polarizer, or if retardation axes of two protective films are insubstantial parallel to each other.

(Adhesive Agent)

An adhesive agent between the polarizer and the protective film mayinclude is not particularly limited, but may include, for example, a PVAresin (including modified PVA such as an acetacetyl group, a sulfonicacid group, a carboxyl group, an oxyalkylene group and so on) and aboron compound aqueous solution, preferably the PVA resin. The thicknessof the adhesive layer is preferably 0.01 to 10 μm, particularlypreferably 0.05 to 5 μm.

(Integrated Manufacturing Process of Polarizer and Protective Film)

It is preferable that the polarizing plate for the liquid crystaldisplay of the invention is manufactured by expanding and contracting apolarizer, lowering its volatility fraction to dry the polarizer,laminating a protective film on at least one side of the polarizerduring or after drying, and then post-heating the polarizer and theprotective film. When the protective film is also used as an opticalcompensation film functioning as an optical compensation layer or a basefilm of a light diffusion layer, it is preferable that the protectivefilm having the light diffusion layer at its one side and thetransparent base film having the optical compensation film at a sideopposite to the protective film are laminated each other and arepost-heated.

An example of the lamination method may include a method of laminatingthe protective film on the polarizer using an adhesive, with both endsof the polarizer fixed, during drying of the polarizer, and thenear-notching both ends, a method of releasing the polarizer from a statewhen both ends of the polarizer are fixed after drying of the polarizer,ear-notching both ends and then laminating the protective film on thepolarizer, etc. An example of an ear notch method may include a cuttermethod, a laser method and other known methods. It is preferable to heatthe protective film and the polarizer after the lamination in order todry the adhesive agent and improve polarizability. Heating conditionsare varied depending on the kind of the adhesive agent. In case of awater-base adhesive agent, heating temperature is preferably 30° C. ormore, more preferably 40° C. to 100° C., particularly preferably 50° C.to 90° C. It is particularly preferable from a standpoint of performanceand productivity that these processes are performed in an assembly line.

(Performance of Polarizing Plate)

It is preferable that the polarizing plate comprising the protectivefilm, the polarizer and the light diffusion layer related to theinvention has optical properties and durability (conservation in shortand long terms) which are equivalent or superior to those of availablesuper high contrast products (for example, “HLC2-5618” available fromSanritz Corporation). Specifically, if visible light transmittance is42.5% or more, a polarization degree {(Tp−Tc)/(Tp+Tc)}^(1/2)≧0.9995(where, Tp is parallel transmittance and Tc is perpendiculartransmittance), and the polarizing plate are left alone for 500 hours attemperature of 60° C. under an atmosphere of 90% RH and for 500 hours attemperature of 80° C. under a dry atmosphere, an absolute value of achange rate (%) of light transmittance is preferably 3 or less, morepreferably 1 or less, and an absolute value of a change rate ofpolarization degree is preferably 1 or less, more preferably 0.1 orless.

(Optical Compensation Film)

An optical compensation film is used to alleviate image coloration orextend a viewing angle in a liquid crystal display. In the invention,the optical compensation film is not indispensable, as described above.For example, the optical compensation film is unnecessary if one or bothof a pair of protective films of the polarizing plate have abirefringence property to function as an optical compensation film.

In-plane retardation (Re) of the entire optical compensation film ispreferably 20 to 200 nm Thickness direction retardation (Rth) of theentire optical compensation film is preferably 50 to 500 nm.

An example of the optical compensation film may include an opticalcompensation film formed of an expansible polymer film and an opticalcompensation film formed of a low or high molecule liquid crystalcompound on a transparent base film, both of which may be used in theinvention. An optical compensation film having a stacked structureincluding a two-layered optical compensation film may be used. Inconsideration of thickness of the optical compensation film having thestacked structure, an optical compensation film having a coated-typestacked structure is preferred to an optical compensation film having ahigh molecule expansible film stacked structure.

A high molecule film used for the optical compensation film may be anexpanded high molecule film or combination of a coated-type highmolecule layer and a high molecule film. An example of material of thehigh molecule film may generally include a synthetic polymer (forexample, polycarbonate, polysulfone, polyethersulfone, polyacrylate,polymethacrylate, norbornene resin, triacetylcellulose, etc.).

(Optical Compensation Formed of Liquid Crystal Compound)

Next, an optical compensation film formed of a liquid crystal compoundwill be described in detail.

Since a liquid crystal compound has a variety of alignment states, anoptical compensation film formed of a liquid crystal compound exhibits adesired optical property by a single layer or a multi-layered structure.That is, the optical compensation film may comprise a base film and oneor more layers formed on the base film. Retardation of the entireoptical compensation film may be adjusted by optical anisotropy of theoptical compensation film. In addition, either a low molecule typeoptical compensation film or a high molecule type optical compensationfilm may be used in the invention.

(Optical Compensation Formed of Discotic Liquid Crystal Compound)

A discotic liquid crystal compound may be used as the liquid crystalcompound forming the optical compensation film. It is preferable thatthe discotic liquid crystal compound is aligned substantiallyperpendicular (at an average inclined angle of 50 to 90°) to a polymerfilm plane.

Examples of the discotic liquid crystal compound are disclosed invarious documents (for example, C. Destrade et al, “Mol. Crysr. Liq.Cryst.”, Volume 71, p. 111 (1981); Japanese Chemical Society,“Introduction to Chemistry, published quarterly”, No. 22, “Chemistry ofliquid crystal”, Chapter V, Chapter X Paragraph II (1994); B. Kohne etal, “Angew. Chem. Soc. Chem. Comm.”, p. 1794 (1985); J. Zhang et al, “J.Am. Chem. Soc.”, Volume 116, p. 2655 (1994), etc.). Polymerization of adiscotic liquid crystal compound is disclosed in JP-A-8-27284.

It is preferable that the discotic liquid crystal compound has apolymeric group so that the compound can be fixed by polymerization. Forexample, it may be considered that a polymeric group as a substituent iscombined to a discotic core of a discotic liquid crystal compound.However, if the polymeric group is directly combined to the discoticcore, it is difficult to maintain an alignment state in a polymerizationreaction. In this case, a structure having a linkage group between thediscotic core and the polymeric group is preferable. That it ispreferable that the discotic liquid crystal compound having thepolymeric group is a compound expressed by the following formula (1).D(-L-P)n  formula (1)

In the formula (1), D represents a discotic core, L represents abivalent linkage group, P represents a polymeric group, and n representsan integer of 4 to 12.

Examples of the discotic core (D), the bivalent linkage group (L) andthe polymeric group (P) in the general formula (1) may include (D1) to(D15), (L1) to (L25) and (P1) to (P18), respectively, disclosed inJP-A-2001-4837, the disclosure of which is incorporated herein byreference.

Preferably, these liquid crystal compounds are aligned substantiallyuniformly in the optical compensation film. More preferably, theseliquid crystal compounds are fixed with a substantially uniformalignment state in the optical compensation film. Most preferably, theseliquid crystal compounds are fixed by a polymerization reaction. It ispreferable that the discotic liquid crystal compound having thepolymeric group is substantially perpendicularly aligned. The term‘substantially perpendicularly’ used herein means that an average angle(average inclined angle) between a disk plane of the discotic liquidcrystal compound and a plane of an optical compound film falls within arange of 50° to 90°. The discotic liquid crystal compound may beobliquely aligned, or may have a slowly varying inclined angle (hybridalignment). In case of the oblique alignment or the hybrid alignment, anaverage inclined angle is preferably 50° to 90°.

It is preferable that the optical compensation film is formed byapplying the liquid crystal compound and the following polymerizationinitiator or other additives on an alignment film.

It is preferable that a solvent used to make an application solution isan organic solvent. An example of the organic solvent may include amide(for example, N,N-dimethylformamide), sulfoxide (for example,dimethylsulfoxide), a heterocyclic compound (for example, pyridine),hydrocarbon (for example, benzene, hexane, etc.), alkylhalide (forexample, chloroform, dichloromethane, etc.), ester (for example, aceticacid methyl, acetic acid butyl, etc.), ketone (for example, acetone,methylethylketone, etc.), ether (for example, tetrahydrofuran,1,2-dimethoxyethane, etc.), etc., preferably the alkylhalide and theketone. Two or more kinds of organic solvents may be used incombination. The application solution may be applied by known methods(for example, an extrusion coating method, a direct gravure coatingmethod, a reverse gravure coating method, a die coating method, etc.).

(Fixation of Alignment State of Liquid Crystal Compound)

It is preferable that an aligned liquid crystal compound is fixed whilemaintaining its alignment state. It is preferable that the alignedliquid crystal compound is fixed by a polymerization reaction of apolymeric group introduced into the liquid crystal compound. Thepolymerization reaction includes a thermal polymerization reaction usinga thermal polymerization initiator and a photopolymerization reactionusing a photopolymerization initiator, preferably thephotopolymerization reaction. An example of the photopolymerizationinitiator may include a α-carbonyl compound (for example, ones disclosedin U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloinether (for example,one disclosed in U.S. Pat. No. 2,448,828), a α-hydrocarbon-substitutedaromatic acyloin compound (for example, one disclosed in U.S. Pat. No.2,722,512), a polynuclear quinone compound (for example, ones disclosedin U.S. Pat. Nos. 3,046,127 and 2,951,758), combination oftriarylimidazoledimer and p-amino phenylketone (for example, onedisclosed in U.S. Pat. No. 3,549,367), an acridine and fenadine compound(for example, ones disclosed in JP-A-60-105667 and U.S. Pat. No.4,239,850), and an oxadiazole compound (for example, one disclosed inU.S. Pat. No. 4,212,970).

Usage of the photopolymerization initiator is preferably 0.01 to 20 wt%, more preferably 0.5 to 5 wt % of solid of the application. It ispreferable that an ultraviolet ray is used for radiation forpolymerization of the liquid crystal compound. Radiation energy ispreferably 20 mJ/cm² to 50 J/cm², more preferably 100 to 800 mJ/cm². Theradiation may be carried out under heating conditions in order topromote the photopolymerization reaction. The thickness of the opticalcompensation film is preferably 0.1 to 10 μm, more preferably 0.5 to 5μm.

(Alignment Film)

When the optical compensation film is formed, it is preferable to use analignment film in order to align the liquid crystal compound. Thealignment layer may be prepared by means of a rubbing treatment of anorganic compound (preferably a polymer), oblique deposition of aninorganic compound, formation of a layer having a micro group, oraccumulation of an organic compound (for example, ω-tricosane,dioctadecyldimethylammoniumchloride, stearyl acid methyl, etc.) by anLangmuir-Blodgett method (BL film). In addition, alignment films havingan alignment function by application of an electric field or a magneticfield, or light radiation. An alignment film formed by a rubbingtreatment of a polymer is particularly preferable.

The rubbing treatment is performed by rubbing a surface of a polymerlayer several times in a constant direction with paper or fabric. Thekind of the polymer used in the alignment film depends on alignment(particularly an average inclined angle) of the liquid crystal compound.For example, a polymer not to lower surface energy of the alignment film(an ordinary polymer for alignment) is used to align the liquid crystalcompound horizontally. Examples of kinds of the polymer for a liquidcrystal cell or an optical compensation film are disclosed in variousdocuments. It is preferable that any alignment film has a polymericgroup to enhance adhesion between the liquid crystal compound and atransparent support. It is preferable to use an alignment film forming achemical bond with the liquid crystal compound at an interfacetherebetween, as disclosed in JP-A-9-152509.

The thickness of the alignment film is preferably 0.01 to 5 μm, more ispreferably 0.01 to 1 μm.

In addition, after the liquid crystal compound is aligned using thealignment film, an optical compensation film may be formed by fixing theliquid crystal compound while maintaining the alignment state, andtransferred into the transparent base film.

A base film to support the optical compensation film is not particularlylimited, but may be one of various polymer films, for example,triacetylcellulose, norbornene resin, etc. In addition, as describedabove, the protective film of the polarizing plate may be also used as asupport of the optical compensation film. Examples of material of thebase film in this aspect are the same as the examples of material of theprotective film of the polarizing plate, as described above.

EXAMPLES Example 1

A liquid crystal display shown in FIG. 1 is manufactured. Specifically,the upper polarizing plate 1, the upper optical compensation film 14,the liquid crystal cell (the upper substrate 5, the liquid crystalmolecules 6 contained in the liquid crystal layer, the lower substrate7), the lower optical compensation film 24, and the lower polarizingplate 2 are stacked from an observation direction (top side). Inaddition, the backlight unit (not shown) using a cold cathodefluorescent lamp or the like is disposed below the lower polarizingplate.

Hereinafter, a method of manufacturing the members used will bedescribed.

(Manufacture of ECB Mode Liquid Crystal Cell)

For the liquid crystal cell, a liquid crystal material having positivedielectric anisotropy is drop-injected and sealed between thesubstrates, with a cell gap of 3.5 μm, and Δn·d of the liquid crystallayer 7 is set to be 300 nm. As the liquid crystal material, liquidcrystals having positive anisotropy and refractive index anisotropy ofΔn=0.0854 (589 nm, 20° C.) and Δ∈=+8.5 (for example, MLC-9100 availablefrom Merck, Co., Ltd.) are used. An intersection angle of the liquidcrystal cell is 0°, and, when the liquid crystal cell is laminated onthe upper and lower polarizing plates later, the rubbing directions(alignment control directions) of the upper and lower substrates of theliquid crystal cell intersect a support retardation axis (in parallel toan expansion direction) by 45°. A polarizing plate absorption axisinterests the liquid crystal cell alignment directions (rubbingdirections) by about 45°, and an intersection angle between absorptionaxes of the upper and lower polarizing plates is about 90°, which iscross Nicol.

(Manufacture of Celluloseacetate Film)

A celluloseacetate solution is prepared by heating and agitating thefollowing compositions put into a mixing tank and dissolving componentsof the compositions.

(Composition of Celluloseacetate Solution)

Celluloseacetate having acidity of 60.7 to 61.1% 100 parts by weightTriphenylphosphate (plasticizer) 7.8 parts by weightBiphenyldiphenylphosphate (plasticizer) 3.9 parts by weightMethylenechloride (first solvent) 336 parts by weight Methanol (secondsolvent) 29 parts by weight 1-buthanol (third solvent) 11 parts byweight

The obtained dope is expanded using a band expander. A celluloseacetatefilm (80 μm thick) having remaining solvent of 0.3 wt % is prepared bydrying a film on a band with warm wind of 70° C. after the temperatureof the film surface reaches 40° C. and then again drying the film withdrying wind of 140° C. Re and Rth values for a wavelength of 546 nm aremeasured for the prepared celluloseacetate film (transparent support andprotective film) according to the above-described methods. As a resultof the measurement, Re is 3 nm and Rth is 8 nm.

The prepared celluloseacetate film is digested into a potassiumhydroxide solution (25° C.) of 2.0 mol/L for two minutes, neutralizedwith sulfuric acid, washed with pure water, and then dried. Surfaceenergy of the celluloseacetate film is measured by a contact method. Asa result of the measurement, the surface energy is 63 mM/m. In thismanner, the celluloseacetate film for the protective film ismanufactured.

(Manufacture of Alignment Film for Optical Compensation Film)

An application solution having the following compositions is applied onthe celluloseacetate film using a #16 wire bar coater. The applicationsolution is dried for 60 seconds with warm wind of 60° C., and thenagain for 150 seconds with warm wind of 90° C. Next, the formed film issubjected to a rubbing treatment in the same direction as an in-planeretardation axis (in parallel to an expansion direction) of thecelluloseacetate film.

(Composition of Alignment Film Application Solution)

Following modified polyvinylalcohol 20 parts by weight Water 360 partsby weight Methanol 120 parts by weight Glutaraldehyde (plasticizer) 1.0parts by weightModified Polyvinylalcohol

(Manufacture of Optical Compensation Film)

On the alignment film is applied an application solution in which thefollowing discotic liquid crystal compound of 91.0 g, ethyleneoxidemodified trimethylolpropanetriacrylate (V#360 available from OSAKAORGANIC CHEMICAL INDUSTRY LTD.) of 9.0 g, celluloseacetatebutylate(CAB551-0.2 available from Eastman Chemical Company) of 2.0 g,celluloseacetatebutylate (CAB531-1 available from Eastman ChemicalCompany) of 0.5 g, photopolymerization initiator (IRGACURE 907 availablefrom Nihon Ciba-Geigy K.K.) of 3.0 g, and intensifier (KAYACURE DETXavailable from Nippon Kayaku Co., Ltd) of 1.0 g are dissolved intomethylethylketone of 414 g, at 6.2 ml/m² (6.2 cc/m²) using a #3.6 wirebar. This application solution is heated for two minutes in a constanttemperature zone of 130° C. to align the discotic liquid crystalcompound. Next, the discotic liquid crystal compound is polymerized bymeans of UV radiation for one minute at temperature of 60° C. using ahigh pressure mercury lamp of 120 W/cm. Thereafter, the temperaturedecreases to a room temperature, and then the optical compensation filmis formed.

Discotic Liquid Crystal Compound

In the formed optical compensation film, the discotic liquid crystalcompound is hybrid-aligned with an angle of 11° to 66° (inclined angle)between a disk plane and a protective film, which increases from theprotective film to an air interface. The inclined angle is calculated bymeasuring a retardation value while changing an observation angle usingan ellipsometer (M-150 available from JASCO Corporation) according to amethod disclosed in “Design Concepts of the Discotic NegativeBirefringence Compensation Films SID98 DIGEST” with the assumption of arefractive index ellipsoid.

(Manufacture of Elliptical Polarizing Plate)

A polarizer is manufactured by absorbing iodine into an expandedpolyvinylalcohol film, and the formed optical compensation film islaminated on one side of the polarizer at a support plane using apolyvinylalcohol adhesive. In addition, a 80 μm thickcellulosetriacetate film (TD-80U available from FUJIFILM Corporation) issubjected to a saponification treatment, and is laminated on a sideopposite to the liquid crystal cell of the polarizer using apolyvinylalcohol adhesive. The absorption axis of the polarizer and theretardation axis (in parallel to the expansion direction) of the supportof the optical compensation film are arranged in parallel to each other.In this manner, the polarizing plate is manufactured.

In addition, with respect to a horizontal direction of the displaydevice, an axial angle of the absorption axis of the polarizer of theupper polarizing plate is set to be 45°, the alignment control direction(rubbing direction) of the upper optical compensation film is set to be45°, the alignment control direction (rubbing direction) of the liquidcrystal cell upper substrate is set to be 90°, an axial angle of thelower polarizing plate is set to be 135°, the alignment controldirection of the lower optical compensation film is set to be 135°, andthe alignment control direction (rubbing direction) of the liquidcrystal cell lower substrate is set to be 270°.

(Application of Light Diffusion Layer)

(Light Diffusion Layer HC-01A)

A translucent resin forming a light diffusion layer is obtained bydissolving a mixture of a zirconium oxide ultrafine particledispersion-containing hard coat application solution (DeSolite Z7404available from JSR Corporation) of 100 parts by weight and a translucentresin DPHA (available from Nippon Kayaku Corporation; a mixture ofdipentaerythritolhexaacrylate and dipentaerythritolpentaacrylate) of 57parts by weight in a methylethylketone/methylisobutylketone (20/80weight ratio) solution and applying and UV-curing the mixture. Arefractive index of the obtained translucent resin is 1.61. A mixture ofcross-linked polymethylmethacrylate beads (MX150 having a diameter of1.5 μm and a refractive index of 1.49, which is available from SokenChemical & Engineering Co., Ltd.) of 17 parts by weight and cross-linkedpolymethylmethamylate beads (MX300 having a diameter of 3.0 μm and arefractive index of 1.49, which is available from Soken Chemical &Engineering Co., Ltd.) of 7 parts by weight as translucent particles isdissolved into the methylethylketone/methylisobutylketone (20/80 weightratio) solution to have solid of 50%. This solution having the solid of50% is applied on a triacetylcellulose film (TD-80U available fromFUJIFILM Corporation) at side opposite to the optical compensation filmof the elliptical polarizing plate, with the polarizer interposedtherebetween, with the application amount of 1.5 μmpolymethylmethacrylate beads of 0.42 g/m², dried for 15 seconds at 30°C. and for 20 seconds at 90° C., and then cured by means of radiation ofan ultraviolet ray of 50 mJ/cm² using an air cooling metalhalide lamp(available from EYEGRAPHICS CO., LTD.) of 160 W/cm under a nitrogenfuzzy atmosphere (oxygen concentration: 100 ppm). Thus, a polarizingplate having the light diffusion layer HC-01A is manufactured. Thethickness of a dried film of the light diffusion layer is 3.0 μm.

(Light Diffusion Layer Hc-02A to 11A)

Except that the application amount of 1.5 μm polymethylmethacrylatebeads of the light diffusion layer is changed, Light diffusion layersHC-02A˜11A are manufactured in a manner similar to the light diffusionlayer HC-01A. The application amount of 1.5 μm polymethylmethacrylatebeads is as shown in a table which will be described later.

(Light Diffusion Layer HC-01B)

A translucent resin forming a light diffusion layer is obtained bydissolving and diluting a mixture of a DPHA (available from NipponKayaku Corporation) of 14.79 parts by weight and a PET-30 (availablefrom Nippon Kayaku Corporation; a mixture of pentaerythritoltriacrylateand pentaerythritoltetraacrylate) of 133.11 parts by weight into asolution and applying and UV-curing the mixture. A refractive index ofthe obtained translucent resin is 1.53. A beads dispersion solution of7.7 parts by weight in which highly cross-linked polystyrene beads(SBX-8 having a diameter of 8 μm and a refractive index of 1.62, whichis available from SEKISUI PLASTICS Co., Ltd.) as translucent particlesare adjusted to have beads solid of 30% with cyclohexanone, a beadsdispersion solution of 17.97 parts by weight in which cross-linkedpolystyrene beads (SX130H having a diameter of 1.3 μM and a refractiveindex of 1.61, which is available from Soken Chemical & Engineering Co.,Ltd.) are adjusted to have beads solid of 30% with cyclohexanone, apolymerization initiator of 6 parts by weight (IRGACURE 184 availablefrom Chiba Specialty Chemicals), a polymerization initiator of 1.06parts by weight (IRGACURE 907 available from Chiba Specialty Chemicals),a silicon leveling agent of 0.22 parts by weight (FZ2191 available fromNippon Unicar Company Limited), toluene of 133.5 parts by weight, andcyclohexanone of 39.2 parts by weight are mixed in the resin solution tohave solid of 46%. This solution having the solid of 46% is applied on atriacetylcellulose film (TD-80U available from FUJIFILM Corporation) atside opposite to the optical compensation film of the ellipticalpolarizing plate, with the polarizer interposed therebetween, with thelayer thickness of 20 μm, dried for 15 seconds at 30° C. and for 20seconds at 90° C., and then cured by means of radiation of anultraviolet ray of 50 mJ/cm² using an air cooling metalhalide lamp(available from EYEGRAPHICS Co., LTD.) of 160 W/cm under a nitrogenfuzzy atmosphere (oxygen concentration: 100 ppm). Thus, a polarizingplate having the light diffusion layer HC-01B is manufactured. Theapplication amount of the 1.3 μm cross-linked polystyrene beads is 1.1g/m².

(Light Diffusion Layer HC-01C)

A translucent resin forming a light diffusion layer is obtained bydissolving a mixture of a silica ultrafine particledispersion-containing hard coat application solution (DeSolite Z7526available from JSR Corporation) of 100 parts by weight, cross-linkedpolystyrene beads (SX130H having a diameter of 1.3 μm and a refractiveindex of 1.61, which is available from Soken Chemical & Engineering Co.,Ltd.) of 25 parts by weight as translucent particles, and cross-linkedpolystyrene beads (SX350H having a diameter of 3.5 μm and a refractiveindex of 1.61, which is available from Soken Chemical & Engineering Co.,Ltd.) of 6 parts by weight into a methylethylketone/methylisobutylketone(20/80 weight ratio) solution to have solid of 45%. This solution havingthe solid of 45% is applied on a triacetylcellulose film (TD-80Uavailable from FUJIFILM Corporation) at side opposite to the opticalcompensation film of the elliptical polarizing plate, with the polarizerinterposed therebetween, with the application amount of 1.3 μmpolystyrene beads of 0.9 g/m², dried for 15 seconds at 30° C. and for 20seconds at 90° C., and then cured by means of radiation of anultraviolet ray of 50 mJ/cm² using an air cooling metalhalide lamp(available from EYEGRAPHICS CO., LTD.) of 160 W/cm under a nitrogenfuzzy atmosphere (oxygen concentration: 100 ppm). Thus, a polarizingplate having the light diffusion layer HC-01C is manufactured. Thethickness of a dried film of the light diffusion layer is 3.0 μm.

(Light Diffusion Layer HC-01D)

Except that (1) the highly cross-linked polystyrene beads (SBX-8 havinga diameter of 8 μm and a refractive index of 1.62, which is availablefrom SEKISUI PLASTICS Co., Ltd.) is replaced with highly cross-linkedpolystyrene beads (SBX-6 having a diameter of 6 μm and a refractiveindex of 1.62, which is available from SEKISUI PLASTICS Co., Ltd.) and(2) the thickness of the dried film of the light diffusion layer ischanged from 20 μm to 5.5 μm, a light diffusion layer HC-01D ismanufactured in the same similar as the light diffusion layer HC-01B.

In addition, (3) the application amount of 1.3 μm polystyrene beads isas shown in a table which will be described later to manufacture lightdiffusion layers HC-02D to 04D.

(Application of Low Refractive Layer)

(Preparation of Sol Solution (a))

In a reactor having an agitator and a reflux condenser, a sol solutionis obtained by mixing methylethylketone of 119 parts by weight,3-acryloyloxypropyltrimethoxysilane of 101 parts by weight (KBM-5103available from Shin-Etsu Chemical Co., Ltd.) anddiisopropoxyaluminumethylacetacetate of 3 parts by weight, adding ionexchange water of 30 wt % to the mixture, reacting the mixture and theion exchange water for 4 hours at 60° C., and cooling resultants to theroom temperature. A weight-average molecule weight of the sol solution(a) is 1600, components having a molecule weight of 1000 to 20000 ofcomponents over oligomer components are 100 wt %. In addition, a gaschromatography analysis shows that there remains noacryloyloxypropyltrimethoxysilane as raw material. Finally, amethylethylketone solution is prepared, and concentration of solid is 29wt %.

(Preparation of Low Refractive Layer Application Solution)

Low refractive layer application solutions LN-1 to LN-3 are adjustedaccording to the following table. Numerals in the table have the unit ofparts by weight.

TABLE 1 APPLICATION SOLUTION RAW MATERIAL LN-1 LN-2 LN-3 FLUORINE-JTA-113 56.5 56.5 — CONTAINING P-3 — — 7.51 BINDER BINDER SOL(a) 1.880.95 0.95 PARTICLE MEK-ST-L 5.57 — HOLLOW SILICA — 7.76 7.76 DISPERSIONSOLUTION INITIATOR PM980M SOLUTION 1.73 1.73 0.87 MP-TRIAZZINE — — 0.09ADDITIVE RMS-033 — — 2.75 SOLVENT METHYLETHYLKETONE 31.5 30.2 72.6CYCLOHEXANONE 2.83 2.83 7.51 TOTAL 100 100 100

The application solutions LN-1 to LN-2 are prepared when they arefiltered by a polypropylene filter having a hole diameter of 1 μm.

Compounds used to prepare the application solutions are as follows.

“JTA-113”: fluorine-containing thermally cross-linkable polymer solutionthat contains silicon, refractive index 1.44, solid concentration 6 wt%, solvent methylethylketone, made by JSR Corporation

“P-3”: fluorine-containing copolymer (P-3) disclosed in JapaneseUnexamined Patent Application Publication No. 2004-45462, weigh-averagemolecule weight about 50000, solid concentration 23.8 wt %, solventmethylethylketone

“MEK-ST-L”: silica particle dispersion solution, average diameter 45 nm,solid concentration 30 wt %, dispersion solvent methylethylketone, madeby NISSAN CHEMICAL INDUSTRIES, LTD

“PM980M solution”: solution in which polymerization initiator PM980Mmade by Wako Pure Chemical Industries, Ltd. is diluted by solventmethylethylketone to have solid concentration of 2 wt %

“MP-triazine”: photopolymerization initiator made by Sanwa Chemical Co.,Ltd.

“RMS-033”: reactive silicon resin made by Gelest Corporation,methylethylketone 6 wt %

“Hollow silica dispersion solution”: CS-60, dispersion solventisopropylalcohol, made by CATALYSIS & CHEMICALS IND. Co., Ltd., hollowsilica particle dispersion solution in which hollow silica particles(surface modification rate: 30 wt % for hollow silica) having arefractive index of 1.31, an average diameter of 60 nm, and a shellthickness of 10 nm are surface-modified by a silane coupling agent(KBM-5103 available from Shin-Etsu Chemical Co, Ltd.), solidconcentration 18.2 wt %

(Application of Low Refractive Index Layer-1)

After various kinds of light diffusion layers of the invention areapplied, the application solutions LN-1 and 2 are wet-applied using abar coater such that the thickness of the dried film of the lowrefractive index layer becomes 95 nm. Subsequently, the low refractiveindex layer is dried for 150 seconds at 120° C. and again for 8 minutesat 100° C., cured by means of radiation of an ultraviolet ray of 110mJ/cm² using an air cooling metalhalide lamp (available from EYEGRAPHICSCo., Ltd.) of 240 W/cm under a nitrogen fuzzy atmosphere (oxygenconcentration: 100 ppm), and then rolled. A refractive index of the lowrefractive index layer is 1.45 for LN-1 and 1.41 for LN-2.

(Application of Low Refractive Index Layer-2)

After various kinds of light diffusion layers of the invention areapplied, the application solution LN-3 is wet-applied using a die coatersuch that the thickness of the dried film of the low refractive indexlayer becomes 95 nm. Subsequently, the low refractive index layer isdried for 70 seconds at 120° C., cured by means of radiation of anultraviolet ray of 400 mJ/cm² using an air cooling metalhalide lamp(available from EYEGRAPHICS Co., Ltd.) of 240 W/cm under a nitrogenfuzzy atmosphere (oxygen concentration: 100 ppm), and then rolled. Arefractive index of the low refractive index layer is 1.38.

Samples 1-1 to 1-20 of the invention and samples of comparative examples1 to 5 are applied based on the following table to prepare lightdiffusion layer attachment films. The sample 1-19 of the invention isone having no refractive index layer of the sample 1-9 of invention, andthe sample 1-20 of the invention is one having no refractive index layerof the sample 1-19 of invention.

(Evaluation of Light Diffusion Film)

The obtained light diffusion films are evaluated for the followingitems.

(1) Integral Reflectivity

Integral reflectivity is measured for an incident angle of 5° in awavelength range of 380 nm to 780 nm using a spectrophotometer “V-550”(available from JASCO Corporation) in which an adapter “ILV-471” ismounted. Average integral reflectivity is calculated to be 450 to 650nm.

(2) Internal Haze

1) A total haze value (H) of the obtained optical film is measured basedon JIS-K7136.

2) Several silicon oil drops are added to both sides of the opticalfilm, and then two sheets of 1 mm thick glass plates (micro slider glasscode S9111 available from MATSUNAMI Corporation) are closely adhered toboth sides of the optical film, respectively. Here, a haze is measuredwith a surface haze removed, and a haze is measured with only siliconoil inserted between the two sheets of glass plates whose haze isseparately measured. An internal haze (Hi) of the film is calculated asa difference between the measured hazes.

3) A surface haze (Hs) is calculated as a difference between the totalhaze (H) and the internal haze (Hi).

(3) Evaluation of scattering light profile

The light diffusion film is arranged perpendicular to incident light anda scattering light profile is measured over all directions using an autoGonio-photometer GP-5 type (available from MURAKAMI COLOR RESEARCHLABORATORY Co., Ltd.). Scattering light intensity of 30° is obtained forlight intensity of emission angle of 0°.

(4) Viewing Angle

For the manufactured liquid crystal display, a viewing angle in an upperdirection is measured in 8 steps from black display (L1) to whitedisplay (L8) using a measuring instrument (EZ-Contrast160D availablefrom ELDIM Corporation).

A contrast ratio is more than 10 and a viewing angle has a range with nogray scale inversion.

Evaluation is made in the following four steps.

O: 76° or more

Δ: 73° or more and less than 76°

Δ×: 70° or more and less than 73°

x: less than 70°

(5) Blur

An image is displayed on the manufacture liquid crystal display and blurof the displayed image is evaluated in four steps.

O: No blur was found out.

O′: A very little blur was found out, but was not remarkable.

Δ: A little blur was recognized.

x: Blur was recognized.

TABLE 2 LIGHT DIFFUSION LAYER APPLICATION AMOUNT OF LOW REFRACTIVEPARTICLES TO LAYER DISPLAY REFRAC- GRANT REFRAC- INTERNAL INTEGRALCHARACTERISTIC TIVE SCATTERING TIVE HAZE I_(30°)/I_(0°) REFLEC- VIEWINGSOLUTION INDEX ABILITY (g/ml) SOLUTION INDEX (%) (%) TIVITY ANGLE BLURSAMPLE 1-1 HC-01A 1.61 0.42 LN-1 1.45 45 0.05 2.2 O O COMPARATIVE HC-02A1.61 0.20 LN-1 1.45 30 0.02 2.2 x O SAMPLE 1-1 COMPARATIVE HC-03A 1.610.36 LN-1 1.45 40 0.04 2.2 Δx O SAMPLE 1-2 SAMPLE 1-2 HC-04A 1.61 0.81LN-1 1.45 55 0.12 2.2 O O SAMPLE 1-3 HC-05A 1.61 1.12 LN-1 1.45 60 0.152.2 O O SAMPLE 1-4 HC-06A 1.61 1.9  LN-1 1.45 70 0.20 2.2 O O SAMPLE 1-5HC-07A 1.61 2.5  LN-1 1.45 75 0.24 2.2 O Δ SAMPLE 1-6 HC-08A 1.61 3.4 LN-1 1.45 80 0.30 2.2 O Δ COMPARATIVE HC-09A 1.61 4.5  LN-1 1.45 90 0.352.2 O x SAMPLE 1-3 SAMPLE 1-7 HC-10A 1.61 1.12 LN-2 1.41 60 0.15 1.4 O OSAMPLE 1-8 HC-11A 1.61 1.12 LN-3 1.38 60 0.15 0.9 O O SAMPLE 1-9 HC-01B1.53 1.10 LN-1 1.45 60 0.14 2.8 O O SAMPLE 1-10 HC-01B 1.53 1.10 LN-21.41 60 0.14 2.0 O O SAMPLE 1-11 HC-01B 1.53 1.10 LN-3 1.38 60 0.14 1.4O O SAMPLE 1-12 HC-01C 1.51 0.90 LN-1 1.45 58 0.13 2.9 O O SAMPLE 1-13HC-01C 1.51 0.90 LN-2 1.41 58 0.13 2.2 O O SAMPLE 1-14 HC-01C 1.51 0.90LN-3 1.38 58 0.13 1.6 O O SAMPLE 1-15 HC-01D 1.53 1.10 LN-1 1.45 60 0.142.8 O O SAMPLE 1-16 HC-01D 1.53 1.10 LN-2 1.41 60 0.14 2.0 O O SAMPLE1-17 HC-01D 1.53 1.10 LN-3 1.38 60 0.14 1.4 O O SAMPLE 1-18 HC-01D 1.530.83 LN-1 1.45 45 0.06 2.8 O O COMPARATIVE HC-01D 1.53 0.73 LN-1 1.45 400.04 2.8 Δx O SAMPLE 1-4 COMPARATIVE HC-01D 1.53 0.55 LN-1 1.45 30 0.022.8 x O SAMPLE 1-5 SAMPLE 1-19 HC-01B 1.53 1.10 = = 60 0.14 4.5 O OSAMPLE 1-20 HC-01D 1.53 0.83 = = 45 0.06 4.5 O O

In the samples 1-1 to 20 of the invention, improvement of a viewingangle characteristic is compatible with reduction of blur.

In addition, in comparison to the samples 1-19 and 20 of the invention,the samples 1-1-18 of the invention are particularly preferable sincethey have integral reflectivity reduced by application of the lowrefractive index layer, improve the viewing angle characteristic, reducethe blur, suppress image intrusion by external light, and provide a highcontrast even in a bright place.

Example 2 Comparative Example 2-1

With the sample 1-1 of the invention in Example 1, without the lightdiffusion layer HC-01A stacked, a liquid crystal display ismanufactured.

Example 2-2 Manufacture of Liquid Crystal Display

With the sample 1-1 of the invention in Example 1, with the liquidcrystal cell modified as follows, a liquid crystal display ismanufactured. In FIG. 2, the absorption axis 12D of the polarizer 12 ofthe upper polarizing plate and the retardation axis 11D of theprotective film 11 of the upper polarizing plate are set to be 90°, theretardation axis 13D of the protective film 13 of the upper polarizingplate is set to be 0°, the absorption axis 22D of the polarizer 22 ofthe lower polarizing plate and the retardation axis 21D of theprotective film 21 of the lower polarizing plate are set to be 0°, thealignment control direction 14RD of the upper optically anisotropiclayer 14 is set to be 45°, and the alignment control direction 24RD ofthe lower optically anisotropic layer 24 is set to be 225°.

In addition, the rubbing direction (alignment axis) 5RD of the upper(observer side) substrate 5 of the liquid crystal cell is set to be 45°,the rubbing direction (alignment axis) 7RD of the lower (backlight side)substrate 7 is set to be 225°, and a twist angle is set to be 0°. Withthe changed configuration, a normally white mode ECB type liquid crystalcell is manufactured. The light diffusion layer HC-01A of the sample 1-1of the invention is stacked on the outermost of this liquid crystaldisplay.

Comparative Example 2-2

With the sample 1-2 of the invention, without the light diffusion layerHC-01A stacked, a liquid crystal display is manufactured.

Example 2-3

With the sample 1-1 of the invention in Example 1, with the TN liquidcrystal cell modified as follows, a liquid crystal display ismanufactured. In FIG. 3, the absorption axis 12D of the polarizer 12 ofthe upper polarizing plate and the retardation axes 11D and 13D of theprotective films 11 and 13 of the upper polarizing plate are set to be45°, the absorption axis 22D of the polarizer 22 of the lower polarizingplate and the retardation axes 21D and 23D of the protective films 21and 23 of the lower polarizing plate are set to be 135°, the alignmentcontrol direction 14RD of the upper optically anisotropic layer 14 isset to be 225°, and the alignment control direction 24RD of the loweroptically anisotropic layer 24 is set to be 315°.

(Manufacture of Liquid Crystal Cell)

For the liquid crystal cell, a liquid crystal material having positivedielectric anisotropy is drop-injected and sealed between thesubstrates, with a cell gap d of 4 μm, and Δn·d of the liquid crystallayer 6 is set to be 410 nm (Δn represents refractive index anisotropyof the liquid crystal material). In addition, the rubbing direction(alignment axis) 5RD of the upper (observer side) substrate 5 of theliquid crystal cell is set to be 45°, the rubbing direction (alignmentaxis) 7RD of the lower (backlight side) substrate 7 is set to be 315°,and a twist angle is set to be 90°. With the changed configuration, a TNtype liquid crystal cell is manufactured. The light diffusion layerHC-01A of the sample 1-1 of the invention is stacked on the outermost ofthis liquid crystal display.

Comparative Example 2-3

For Example 2-3, without the light diffusion layer HC-01A of the sample1-1 of the invention stacked, a liquid crystal display is manufactured.

Example 2-4

For Example 2-3, with the angle between the alignment of the liquidcrystal cell and the absorption axis of the polarizing directionchanged, a TN type liquid crystal display is manufactured.

The absorption axis 12D of the polarizer 12 of the upper polarizingplate and the retardation axes 11D and 13D of the protective films 11and 13 of the upper polarizing plate are set to be 90°, the absorptionaxis 22D of the polarizer 22 of the lower polarizing plate and theretardation axes 21D and 23D of the protective films 21 and 23 of thelower polarizing plate are set to be 0°, the alignment control direction14RD of the upper optically anisotropic layer 14 is set to be 270°, andthe alignment control direction 24RD of the lower optically anisotropiclayer 24 is set to be 180°.

In addition, for the liquid crystal cell, a liquid crystal materialhaving positive dielectric anisotropy is drop-injected and sealedbetween the substrates, with a cell gap d of 4 μm, and Δn·d of theliquid crystal layer 6 is set to be 410 nm (Δn represents refractiveindex anisotropy of the liquid crystal material). In addition, therubbing direction (alignment axis) 5RD of the upper (observer side)substrate 5 of the liquid crystal cell is set to be 45°, the rubbingdirection (alignment axis) 7RD of the lower (backlight side) substrate 7is set to be 315°, and a twist angle is set to be 90°. With the changedconfiguration, a TN type liquid crystal cell is manufactured. The lightdiffusion layer HC-01A of the sample 1-1 of the invention is stacked onthe outermost of this liquid crystal display.

Comparative Example 2-4

For Example 2-4, without the light diffusion layer HC-01A of the sample1-1 of the invention stacked, a liquid crystal display is manufactured.

Example 2-5

With the sample 1-1 of the invention in Example 1, with the opticallyanisotropic layer of the liquid crystal cell replaced with acelluloseacetate film (FUJI TAC TD80UF available from FUJIFILMCorporation) in the following IPS type liquid crystal display, a liquidcrystal display is manufactured.

In FIG. 4, the absorption axis 12D of the polarizer 12 of the upperpolarizing plate and the retardation axes 11D and 13D of the protectivefilms 11 and 13 of the upper polarizing plate are set to be 0°, theabsorption axis 22D of the polarizer 22 of the lower polarizing plateand the retardation axis 21D of the protective film 21 of the lowerpolarizing plate are set to be 90°, the retardation axis 23D of theprotective film 23 of the lower polarizing plate are set to be 0°, andthe alignment control direction 14RD of the upper optically anisotropiclayer 14 is set to be 0°.

In addition, the optically anisotropic layer typically has the sameoptical performance as the protective film used in the polarizing plate,which corresponds to no optically anisotropic layer.

In addition, for the liquid crystal cell, a liquid crystal materialhaving positive dielectric anisotropy is drop-injected and sealedbetween the substrates, with a cell gap d of 4 μm, and Δn·d of theliquid crystal layer 6 is set to be 300 nm (Δn represents refractiveindex anisotropy of the liquid crystal material). In addition, therubbing direction (alignment axis) 5RD of the upper (observer side)substrate 5 of the liquid crystal cell is set to be 270°, the rubbingdirection (alignment axis) 7RD of the lower (backlight side) substrate 7is set to be 90°, and a twist angle is set to be 0°. With the changedconfiguration, an IPS type liquid crystal cell is manufactured. Thelight diffusion layer HC-01A of the sample 1-1 of the invention isstacked on the outermost of this liquid crystal display.

Comparative Example 2-5

For Example 2-5, without the light diffusion layer HC-01A of the sample1-1 of the invention stacked, a liquid crystal display is manufactured.

(Optical Measurement of Manufactured Liquid Crystal Display)

A rectangular wave voltage of 60 Hz is applied to the manufacturedliquid crystal display. A contrast ratio as a transmittance ratio (whitedisplay/black display) and a transmittance viewing angle in equal-spaced8 gray scales between black display (L1) transmittance and white display(L8) transmittance are measured using an apparatus for measuring anoptical performance (EZ-Contrast 160D available from ELDIM Corporation).Table 3 shows an angle range without transmittance inversion of adjacentgray scales in a downward direction and a range angle ratio which ismore than a left to right contrast ratio of 10:1.

In addition, Table 3 shows coloration change (color spots) andcircumferential luminance spots (light leakage) by a viewing angle ofblack display by naked eye observation.

Evaluation of color spots is made as follows.

A color difference between a front viewing angle and an azimuth angle45° polar angle 60° viewing angle is evaluated for panel black displaycharacters. When the color difference is measured using a luminancemeter, in a Luv color coordinate system, if a color difference Δu′v′ isless than 0.02, color spots are not observed by naked eye observation (◯in two-step evaluation). If the color difference Δu′v′ is more than0.02, color spots are observed (Δ in two-step evaluation).

Evaluation of circumferential luminance spots is made as follows.

After the manufactured liquid crystal display is stored in a test roomin 40° 80% RH environments and then is left alone for one hour at a roomtemperature, a black display luminance difference between a panel centerand a center of a long side end portion of a polarizing plate ismeasured. Light leakage on a circular arc at long and short sides of acircumference of the polarizing plate is observed by naked eyes. If theluminance difference is more than 0.4 cd/m², it is perceived asluminance spots of a screen (Δ in three-step evaluation). If theluminance difference is 0.2 to 0.4 cd/m², it is not perceived asluminance spots of a screen (O in three-step evaluation) although lightleakage is observed. If the luminance difference is less than 0.1 cd/m²,neither light leakage nor luminance spots is perceived (⊚ in three-stepevaluation). In addition, the same panel has a contrast ratio of 700 to1 with a luminance difference of 400 cd/m² in white display.

TABLE 3 CELL CONFIGURATION DISPLAY PERFORMANCE LIGHT LOWER GRAYBILATERAL DISPLAY POLARIZING DIFFUSION SCALE INVER- ASYM- COLORLUMINANCE MODE PLATE ANGLE LAYER SION ANGLE METRY SPOT SPOT EXAMPLE 1-1ECB  45°/135° ◯ 50° 1:1 ◯ ◯ COMPARATIVE ECB  45°/135° — 40° 1:1 Δ ΔEXAMPLE 2-1 EXAMPLE 2-2 ECB 90°/0°  ◯ 70° 0.8:1   ◯ ⊚ COMPARATIVE ECB90°/0°  — 60° 0.7:1   Δ ◯ EXAMPLE 2-2 EXAMPLE 2-3 TN  45°/135° ◯ 40° 1:1◯ ◯ COMPARATIVE TN  45°/135° — 30° 1:1 Δ Δ EXAMPLE 2-3 EXAMPLE 2-4 TN90°/0°  ◯ 50° 0.7:1   ◯ ⊚ COMPARATIVE TN 90°/0°  — 40° 0.6:1   Δ ◯EXAMPLE 2-4 EXAMPLE 2-5 IPS  0°/90° ◯ 80° 0.9:1   ◯ ⊚ COMPARATIVE IPS 0°/90° — 80° 0.8:1   Δ ◯ EXAMPLE 2-5

Example 3

Hereinafter, an example to show the effect of the preferred aspect (II)will be described.

(Manufacture of Polarizing Plate 1)

(Manufacture of Celluloseacetate Film)

A celluloseacetate solution is prepared by inputting the followingcompositions into a mixing tank, heating and agitating them to dissolvetheir components.

<Composition of Celluloseacetate Solution>

Celluloseacetate of acidity of 60.9% 100 parts by weight Triphenylphosphate (plasticizer) 8.0 parts by weight Biphenyl diphenyl phosphate(plasticizer) 4.0 parts by weight Methylene chloride (first solvent) 250parts by weight Methanol (second solvent) 20 parts by weight

A retardation enhancement solution is prepared by inputting thefollowing retardation enhancer of 16 parts by weight, methylene chlorideof 80 parts by weight and methanol of 20 parts by weight into adifferent mixing tank, heating and agitating them. A dope is prepared bymixing a celluloseacetate solution of 477 parts by weight with aretardation enhancement solution of 22 parts by weight and sufficientlyagitating them. The addition amount of the retardation enhancer is 3.0parts by weight for celluloseacetate of 100 parts by weight.

Retardation Enhancer

The prepared dope is expanded using a band expander. A film having aremaining solvent of 40 wt % is peeled out of a band, carried whileblowing heated wind of 120° C. and drawing it by 101% in a carryingdirection, and dried while widening it by 3% in a width direction usinga tender. Next, after a tender clip is drawn out, by drying the film for20 minutes with heated wind of 140° C., a celluloseacetate film (107 μmthick) having a remaining solvent of 0.3 wt % is prepared.

The prepared celluloseacetate film is digested in a potassium hydroxidesolution (25° C.) of 2.0 N for 2 minutes, neutralized with sulfuricacid, washed with pure water, dried and saponificated.

(Formation of Alignment)

An application solution having the following compositions is applied onthe prepared celluloseacetate film at 24 ml/m² using a #14 wire barcoater. The application solution is dried for 60 seconds with warm windof 60° C. or for 150 seconds with warm wind of 90° C. Next, the formedfilm is subjected to a rubbing treatment in a direction in parallel to alongitudinal direction of the celluloseacetate film.

<Composition of Alignment Film Application Solution>

The following modified polyvinylalcohol 20 parts by weight Water 360parts by weight Methanol 120 parts by weight Glutaraldehyde(cross-linkage agent) 1.0 parts by weightModified Polyvinylalcohol

(Formation of Optically Anisotropic Layer and Manufacture of OpticalCompensation Sheet)

On the alignment film is applied an application solution in which thefollowing discotic liquid crystal compound of 91.0 g, ethyleneoxidemodified trimethylolpropanetriacrylate (V#360 available from OSAKAORGANIC CHEMICAL INDUSTRY LTD.) of 9.0 g, celluloseacetatebutylate(CAB551-0.2 available from Eastman Chemical Company) of 2.0 g,celluloseacetatebutylate (CAB531-1 available from Eastman ChemicalCompany) of 0.5 g, photopolymerization initiator (IRGACURE 907 availablefrom Nihon Ciba-Geigy K.K.) of 3.0 g, and intensifier (KAYACURE DETXavailable from Nippon Kayaku Co., Ltd) of 1.0 g are dissolved intomethylethylketone of 207 g, at 6.2 cc/m² using a #3.6 wire bar. Thisapplication solution is heated for two minutes in a constant temperaturezone of 130° C. to align the discotic liquid crystal compound. Next, thediscotic liquid crystal compound is polymerized by means of UV radiationfor one minute at temperature of 25° C. using a high pressure mercurylamp of 120 W/cm. Thereafter, the temperature decreases to a roomtemperature. Thus, the optically anisotropic layer is formed and theoptical compensation film is manufactured.

Liquid Crystal Compound

(Manufacture of Polarizing Plate)

A polarizer is manufactured by absorbing iodine into an expandedpolyvinylalcohol film, and the manufactured optical compensation sheetis subjected to the saponification treatment and is laminated on oneside of the polarizer such that the celluloseacetate film lies on thepolarizer. The transmission axis of the polarizer and the retardationaxis of the celluloseacetate film are arranged in parallel to eachother. In addition, a 80 μm thick cellulosetriacetate film (FUJI TACTD80UF available from FUJIFILM Corporation) is subjected to asaponification treatment, and is laminated as a transparent protectivefilm on a side opposite to the polarizer using a polyvinylalcoholadhesive. In this manner, the polarizing plate is manufactured.

(Punching of Polarizing Plate)

End lines of two sheets of manufactured polarizing plates having anabsorption axis direction of 45°, as in the TN mode, are punched.

In addition, polarizing plates are punched at different angles (forexample, 40°, 38°, 35°, 15°, 0°, etc. in long and short sidedirections).

(Manufacture of Adhesive)

A mixture of monomers including n-butylacrylate (BA) of 49.5 parts byweight, acrylic acid (AA) of 10 parts by weight and2-hydroxyethyl(meta)acrylate (2-HEMA) of 0.5 parts by weight is injectedinto a 1000 cc reactor having a cooling apparatus for facilitatingadjustment of temperature by reflowing nitrogen gas used to manufacturea copolymer. In addition, ethyl acetate (EA) of 100 parts by weight as asolvent is injected into the reactor. Next, the reactor is purged for 20minutes with nitrogen gas in order to extrude oxygen gas from thereactor, and while maintaining the reactor at 60° C.,azobisisobutyronitrile (AIBN) of 0.03 parts by weight as a reactioninitiator diluted with ethyl acetate at a concentration of 50% isinjected into the reactor and reacts with the mixture for 10 hours toobtain an acryl polymer finally.

The acryl polymer solution (including about solid of 50%) obtained inthe copolymerization process is well blended. Next, a uniform adhesivelayer of 30 μm is obtained by diluting tolylenediisocyanate adduct(TDI-1) of 1.2 parts by weight of trimethylolpropane as an isocyanatecross linkage agent with ethyl acetate of 10 wt %, mixing the adductwith the ethyl acetate uniformly at a proper concentration inconsideration of coating property, and coating and drying the mixture ona release paper. An absolute value of a photoelastic coefficient of theobtained adhesive layer is −500×10⁻¹²(1/Pa).

(Evaluation of Polarizing Plate)

The obtained adhesive is applied on various kinds of polarizing platesobtained as above to obtain adhesive-attached polarizing plates.

Polarizing plates having different absorption axis directions ofdifferent angles are laminated on both sides of quartz glass,respectively. At this time, the absorption axes of two sheets ofpolarizing plates are perpendicular to each other.

The quartz glass on which the polarizing plates are laminated is driedby a drier at 70° C. for 170 hours. The dried quartz glass is mounted ona backlight in a dark room and is observed by naked eyes to evaluatelight leakage. As a result of the observation, light leakage is observedat circumferences of the polarizing plates. In addition, the amount oflight leakage is measured by measuring a luminance distribution using aluminance meter.

As a result of the measurement, FIG. 4 shows a graph plotting increaseof transmittance of the maximal light leakage portion by a thermotreatment, that is, leakage light transmittance (%) obtained in thesample, for different angles (angles between the absorption axisdirection of the polarizing plate and the end line of the polarizingplate)

From the above result, it can be seen that light leakage due to thermaldistortion is reduced in the polarizing plate punched such that theabsorption axis direction of the polarizing plate intersects the endline of the polarizing plate by 45° in case of a TN mode. Accordingly,it is apparent that light leakage due to thermal distortion of a liquidcrystal display can be reduced when this polarizing plate is used in aconventional TN mode liquid crystal display that did not employ such apolarizing plate.

In addition, after the polarizing plate is attached to a TN mode liquidcrystal panel, symmetry of an actual image is evaluated.

As a result of the evaluation, it can be seen that a polarizing platehaving an intersection angle of 5° or more between one side of thepolarizing plate and the absorption axis direction of the polarizingplate has better image symmetry than a polarizing plate having anintersection angle of less than 5°.

From the above description, it is apparent that a polarizing platehaving an intersection angle of 5° to 40° between the absorption axis ofthe polarizing plate and one side of the polarizing plate is excellentin practical use from a standpoint of reduction of light leakage andsymmetry of a display image.

Example 4

Hereinafter, an example to show the effect of the preferred aspects(III-1) and (III-2) will be described.

Gray scales are evaluated for a normally white mode EBC liquid crystaldisplay (Example 4-1) having the configuration shown in FIG. 10 (wherethe optical compensation films 307 and 314 are formed of discoticcompound-containing liquid crystal compositions and comprise opticallyanisotropic layers having discotic molecules fixed in a hybrid alignmentstate) and having the pixel configuration shown in FIG. 11, and a liquidcrystal display (comparative example 4) having the same configuration asExample 4, except the pixel configuration shown in FIG. 12. FIG. 13shows a result of the evaluation.

FIG. 13 shows a graph in which a horizontal axis represents 0˜255 grayscales normalized with white luminance in front observation and avertical axis represents 0˜255 gray scales normalized with whiteluminance in oblique observation (azimuth angle of 270° and polar angleof 45°). In the graph, a solid line represents gray scales expressed byan ideal liquid crystal display with no dependency of a halftone γcharacteristic on a viewing angle. From FIG. 13, it can be seen that theliquid crystal display of Example 4 in which one pixel is constituted bya plurality of sub pixels has reduced dependency of a halftone γcharacteristic on a viewing angle in comparison to the liquid crystaldisplay of Comparative example 4.

Similarly, gray scales are evaluated for a liquid crystal display(Reference example 4-1) having the same configuration as Example 4,except use of the optical compensation films 307 and 314 in FIG. 10, anda liquid crystal display (Reference example 4-2) having the sameconfiguration as Example 4, except use of uniaxial films as the opticalcompensation films 307 and 314 in FIG. 10. In FIG. 13, assuming that thevertical axis is y and the horizontal axis is x, for x=0 which showsblack display in the front observation, y is about 0.25˜0.55 in theoblique observation. From this result, when the optically anisotropiclayers which are formed of discotic compound-containing liquid crystalcompositions and have discotic molecules fixed in a hybrid alignmentstate are used as the optical compensation films 307 and 314, it can beseen that light leakage in the inclined direction in black display canbe reduced, thereby improving viewing angle contrast.

Example 5

Hereinafter, an example to show the effect of the preferred aspect (IV)will be described.

An optical simulation is performed for the TN mode liquid crystaldisplay shown in FIG. 14 to confirm the effect of the invention. An LCDMaster Ver6.08 (available from Shintech Corporation) is used for opticalcalculation. The liquid crystal cell, the electrodes, the substrates,the polarizing plates and so on may be used as conventional for theliquid crystal display. ZLI-4792 attached to the LCD Master is used as aliquid crystal material. Retardation in the front side of the opticalanisotropic layer is set to be 45 nm, the liquid crystal cell hashorizontal alignment of parallel alignment with a pretilt angle of 4°, acell gap of the substrates is set to be 4 μm, and a liquid crystalmaterial having positive dielectric anisotropy has retardation (that is,the product (Δn·d) of the thickness d (μm) of the liquid crystal layerand the refractive index anisotropy Δn) of 395 nm.

The absorption axis 402 of the polarizer 401 is perpendicular that is,90° assuming a horizontal direction of a screen is 0°) to the C2symmetrical axis, and the absorption axis 2 of the polarizer 416 is inparallel (that is, 0° assuming the horizontal direction of the screen is0°) to the C2 symmetrical axis. In addition, a front Re retardationvalue of a pair of first optically anisotropic layers 405 a and 412 aarranged at an inner side of the polarizer is set to be 30 nm, an anglebetween the alignment control directions 406 a and 413 a of the firstoptically anisotropic layers 405 a and 412 a and the alignment controldirections of the liquid crystal layer, respectively, is set to be 0°.That is, in FIG. 14, an angle between the alignment control directions406 a and 408 and an angle between the alignment control directions 413a and 411 are set to be 0°. In addition, a front Re retardation value ofa pair of second optically anisotropic layers 405 b and 412 b arrangedat upper and lower sides of the liquid crystal layer is set to be 30 nm,an angle between the alignment control directions 406 b and 413 b of thesecond optically anisotropic layers and the alignment control directionsof the liquid crystal layer, respectively, is set to be 45°. That is, inFIG. 14, an angle between the alignment control directions 406 b and 407and an angle between the alignment control directions 413 b and 411 areset to be 45°. That is, in this example, the alignment control direction406 b of the upper second optically anisotropic layer 405 b is set to be270° and the alignment control direction 413 b of the lower secondoptically anisotropic layer 412 b is set to be 90°.

In addition, the transparent layers 403 and 414 comprise a transparentlayer having Re of 55 nm and Rth of 120 nm, and an in-plane retardationaxis of the transparent film is coincident with a transmission axis ofadjacent polarizers 401 and 416. G1220DU attached to the LCD Master isused for the polarizer. Re and Rth values of the transparent film for awavelength are set as shown in Example 1 of Table 1. A backlightattached to the LCD Master is used as a light source. With thisconfiguration, an optical characteristic of the liquid crystal displayshown in FIG. 1 is calculated by the LCD Master.

Comparative Example 5

An optical characteristic of a liquid crystal display having the sameconfiguration as in Example, except the first optically anisotropiclayers 405 a and 412 a, the second optically anisotropic layers 405 band 412 b, and the transparent layers 403 and 414, is calculated by theLCD Master.

<Viewing Angle Characteristic (Gray Scale Property) in HorizontalDirection of Liquid Crystal Display>

FIGS. 23 and 24 show graphs plotting contrast contours in all viewingangle directions when a black voltage is applied to the liquid crystaldisplays of Comparative example 5 and Example 5. FIG. 23 shows acontrast contour of Comparative example 5 and FIG. 24 shows a contrastcontour of Example 5.

From FIGS. 23 and 24, it can be seen that conventional Comparativeexample 5 shows poor bilateral symmetry and a generally deterioratedcontrast viewing angle characteristic. In contrast to Comparativeexample 5, Example 5 has remarkably excellent bilateral symmetry andlarge contrast values over a wide range, thereby greatly improving thecontrast viewing angle characteristic.

A TN mode liquid crystal display having the configuration of Example 5is actually manufactured. In the manufactured liquid crystal display, animage having a high contrast in the front and oblique directions isobserved. In addition, this liquid crystal display is stored in a testroom in temperature 40° and humidity 80% environments for 24 hours, andthen is left alone for one hour at a room temperature. In black display,in this liquid crystal display, light leakage out of a circumference ofa polarizing plate is not observed at all by naked eyes.

Example 6-1

(Manufacture of ECB Mode Liquid Crystal Cell)

Hereinafter, an example to show the effect of the preferred aspect (V)will be described.

A liquid crystal cell manufactured by vacuum-injecting and sealing aliquid crystal material having positive dielectric anisotropy betweenopposite substrates with a cell gap of 3.5 μm is used as an ECB modeliquid crystal cell. Δn·d of this liquid crystal layer is set to be240˜310 nm. As the liquid crystal material, liquid crystals havingpositive anisotropy and refractive index anisotropy of Δn=0.0854 (589nm, 20° C.) and Δ∈=+8.5 (for example, MLC-9100 available from Merck,Co., Ltd.) are used. An intersection angle of the liquid crystal cell is0°, and, when the liquid crystal cell is laminated on the upper andlower polarizing plates later, the rubbing directions (alignment controldirections) of the upper and lower substrates of the liquid crystal cellintersect an in-plane retardation axis (in parallel to an expansiondirection) of a biaxial celluloseacylate film by 45°. A polarizing plateabsorption axis interests the liquid crystal cell alignment directions(rubbing directions) by about 45°, and an intersection angle betweenabsorption axes of the upper and lower polarizing plates is about 90°,which is cross Nicol.

Two sheets of polarizing plates are manufactured by laminating anavailable celluloseacylate film on one side of a polarizer andlaminating a biaxial celluloseacylate film (Re=35 nm and Rth=175 nm)made by bi-axially expanding a celluloseacetate film on the other sideof the polarizer, with an in-plane retardation axis of the biaxialcelluloseacylate film perpendicular or in parallel to an absorption axisof the polarizer. A retardation layer is formed by forming an alignmentfilm on a surface of the biaxial celluloseacylate film of one of thepolarizing plates, aligning discotic molecules by applying a polymericcomposition containing a discotic liquid crystal compound to a surfaceof the alignment film, and fixing the alignment state by polymerization.

An ECB mode liquid crystal display is manufactured by laminating thebiaxial celluloseacylate film of one of the two polarizing plates on oneside of the manufactured ECB mode liquid crystal cell and laminating theretardation layer, which is manufactured using the discotic liquidcrystal compound, of the other of the two polarizing plates on the otherside of the ECB mode liquid crystal cell. It is observed that themanufactured liquid crystal display shows ideal black image display inboth of front and oblique directions.

Example 6-2

(Manufacture of ECB Mode Liquid Crystal Cell)

A liquid crystal cell manufactured by vacuum-injecting and sealing aliquid crystal material having positive dielectric anisotropy betweenopposite substrates with a cell gap of 3.0 μm is used as an ECB modeliquid crystal cell. Δn·d of this liquid crystal layer is set to be 300nm. As the liquid crystal material, liquid crystals having positiveanisotropy and refractive index anisotropy of Δn=0.098 (589 nm, 29° C.)and Δ∈=+5.2 are used. An intersection angle of the liquid crystal cellis 0°, and, when the liquid crystal cell is laminated on the upper andlower polarizing plates later, the rubbing directions (alignment controldirections) of the upper and lower substrates of the liquid crystal cellintersect a polarizing plate absorption axis by about 45°, and anintersection angle between absorption axes of the upper and lowerpolarizing plates is about 90°, which is cross Nicol.

A cellulosetriacetate film (TD-80U available from FUJIFILM Corporation,Rth≈40 nm, Re≈1.6 nm) is laminated on surfaces of both of polarizers.Two sheets of polarizing plates are manufactured by forming retardationlayers by forming an alignment film on a surface of the film, aligningdiscotic molecules by applying a polymeric composition containing adiscotic liquid crystal compound to a surface of the alignment film, andfixing the alignment state by polymerization.

An ECB mode liquid crystal display is manufactured by laminating theretardation layers, which are manufactured using the discotic liquidcrystal compound, of the two polarizing plates on both sides of the ECBmode liquid crystal cell, respectively. It is observed that themanufactured liquid crystal display shows ideal black image display inboth of front and oblique directions.

Example 6-3

(Manufacture of ECB Mode Liquid Crystal Cell)

A liquid crystal cell manufactured by vacuum-injecting and sealing aliquid crystal material having positive dielectric anisotropy betweenopposite substrates with a cell gap of 2.8 μm is used as an ECB modeliquid crystal cell. Δn·d of this liquid crystal layer is set to be 280nm. As the liquid crystal material, liquid crystals having positiveanisotropy and refractive index anisotropy of Δn=0.098 (589 nm, 20° C.)and Δ∈=+5.2 are used. An intersection angle of the liquid crystal cellis 0°, and, when the liquid crystal cell is laminated on the upper andlower polarizing plates later, the rubbing directions (alignment controldirections) of the upper and lower substrates of the liquid crystal cellintersect an in-plane retardation axis (in parallel to an expansiondirection) of a biaxial celluloseacylate film by 45°. A polarizing plateabsorption axis interests the liquid crystal cell alignment directions(rubbing directions) by about 45°, and an intersection angle betweenabsorption axes of the upper and lower polarizing plates is about 90°,which is cross Nicol.

A cellulosetriacetate film (TD-80U available from FUJIFILM Corporation,Rth≈40 nm) is laminated on surfaces of both of polarizers. One sheet ofpolarizing plate is manufactured by forming a retardation layer byforming an alignment film on a surface of the cellulosetriacetate film,aligning discotic molecules by applying a polymeric compositioncontaining a discotic liquid crystal compound to a surface of thealignment film, and fixing the alignment state by polymerization. Inaddition, one sheet of polarizing plate is manufactured by laminating anavailable celluloseacylate film on one side of a polarizer andlaminating a biaxial celluloseacylate film (Re=30 nm and Rth=140 nm)made by bi-axially expanding a celluloseacetate film on the other sideof the polarizer, with an in-plane retardation axis of the biaxialcelluloseacylate film perpendicular or in parallel to an absorption axisof the polarizer.

The two sheets of manufactured polarizing plates are laminated on bothsurfaces of the manufactured ECB mode liquid crystal cell, respectively.The retardation layer, which is manufactured using the discotic liquidcrystal compound, of the polarizing plate is laminated on one side ofthe liquid crystal cell, and the biaxial celluloseacylate film of thepolarizing plate is laminated on the other side of the liquid crystalcell. In this manner, an ECB mode liquid crystal display ismanufactured. It is observed that the manufactured liquid crystaldisplay shows ideal black image display in both of front and obliquedirections.

Example 6-4

(Manufacture of ECB Mode Liquid Crystal Cell)

A liquid crystal cell manufactured by vacuum-injecting and sealing aliquid crystal material having positive dielectric anisotropy betweenopposite substrates with a cell gap of 3 μm is used as an ECB modeliquid crystal cell. Δn·d of this liquid crystal layer is set to be 300nm. As the liquid crystal material, liquid crystals having positiveanisotropy and refractive index anisotropy of Δn=0.098 (589 nm, 20° C.)and Δ∈=+5.2 are used. An intersection angle of the liquid crystal cellis 0°, and, when the liquid crystal cell is laminated on the upper andlower polarizing plates later, the rubbing directions (alignment controldirections) of the upper and lower substrates of the liquid crystal cellintersect a support retardation axis (in parallel to an expansiondirection) by 45°. A polarizing plate absorption axis interests theliquid crystal cell alignment directions (rubbing directions) by about45°, and an intersection angle between absorption axes of the upper andlower polarizing plates is about 90°, which is cross Nicol.

One sheet of polarizing plate is manufactured by laminating an availablecelluloseacylate film on one side of the polarizer and laminating a lowretardation celluloseacetate (TAC) film (specifically, Re=1.5 nm (550 nmand Rth=−6 (550 nm), a film manufactured according to a method disclosedin Japanese Unexamined Patent Application Publication No. 2006-30937) onthe other side of the polarizer. In addition, an availablecelluloseacylate film is laminated on one side of the polarizer and abiaxial cellulosetriacetate film (Re=38 nm and Rth=178 nm) made bybi-axially expanding a cellulosetriacetate film is laminated on theother side of the polarizer. In addition, one sheet of polarizing plateis manufactured by forming a retardation layer by forming an alignmentfilm on a surface of the biaxial TAC film, aligning discotic moleculesby applying a polymeric composition containing a discotic liquid crystalcompound to a surface of the alignment film, and fixing the alignmentstate by polymerization.

The two sheets of manufactured polarizing plates are laminated on bothsurfaces of the manufactured ECB mode liquid crystal cell, respectively.The low retardation TAC film of the polarizing plate is laminated on oneside of the liquid crystal cell, and the retardation layer, which ismanufactured using the discotic liquid crystal compound, of thepolarizing plate is laminated on the other side of the liquid crystalcell. In this manner, an ECB mode liquid crystal display ismanufactured. It is observed that the manufactured liquid crystaldisplay shows ideal black image display in both of front and obliquedirections.

Example 6-5

FIG. 29 shows a relationship between average black transmittance inpolar 80° upper, lower, left and right directions in black image displayand Rth when the second retardation layer manufactured using thediscotic liquid crystal compound is laminated on only one polarizingplate (where, the summation Re of the first retardation layer and theprotective TAC film=36.6 inn) for the liquid crystal display having thesame configuration as in Example 6. From the graph of FIG. 29, it can beseen that black transmittance becomes small, and accordingly, highercontrast is obtained if Rth(550) of the retardation layer satisfies arelationship of 0 nm<Rth(550)<330 nm, in comparison to a case wherethere is no retardation layer (that is, Rth=0). The same effect as inFIG. 5 is obtained over the entire range of 0 nm<Rth(550)<70 nm

Example 6-6

FIG. 30 shows a relationship between average black transmittance inpolar 80° upper, lower, left and right directions in black image displayand Rth when the second retardation layer manufactured using thediscotic liquid crystal compound is laminated on both polarizing plates(where, the summation Re=3.2 nm) for the liquid crystal display havingthe same configuration as in Example 6-2. From the graph of FIG. 30, itcan be seen that black transmittance becomes small if Rth(550) of theretardation layer satisfies a relationship of 0 nm<Rth(550)<200 nm, incomparison to a case where there is no retardation layer (that is,Rth=0). The same effect as in FIG. 30 is obtained over the entire rangeof 0 nm<Rth(550)<70 nm.

Example 7

Hereinafter, an example to show the effect of the preferred aspect (VI)will be described.

Reference Example 7-1

A liquid crystal display having the configuration shown in FIG. 34 ismanufactured. Specifically, an upper (elliptical) polarizing plate(protective film 601, polarizer 603, protective film 605 (also used asan optical compensation sheet support), and optically anisotropic layer607), a liquid crystal cell (upper substrate 609, liquid crystal layer611, lower substrate 612), and a lower (elliptical) polarizing plate(optically anisotropic layer 614, protective 616 (also used as anoptically compensation sheet support), polarizer 618, and protectivefilm 620) are stacked from an observation direction (top side). Inaddition, a backlight unit (not shown) using a cold cathode fluorescentlamp or the like is disposed below the lower polarizing plate.

Hereinafter, a method of manufacturing the members used will bedescribed.

(Manufacture of Liquid Crystal Cell)

For the liquid crystal cell, a liquid crystal material having positivedielectric anisotropy is drop-injected and sealed between thesubstrates, with a cell gap (d) of 4 μm, and Δn·d of the liquid crystallayer 611 is set to be 410 nm (Δn is refractive index anisotropy of theliquid crystal material). In addition, a rubbing direction 610 of theupper (observer side) substrate 609 of the liquid crystal cell is 90°, arubbing direction 613 of the lower (backlight side) substrate 612 is 0°,and a twist angle is 90°. In this manner, a TN mode liquid crystal cellis manufactured.

In addition, an absorption axis 604 of the upper polarizing platepolarizer 603 and retardation axes 602 and 606 of the upper polarizingplate protective films 601 and 605 are set to 90°, an absorption axis619 of the lower polarizing plate polarizer 618 and retardation axes 617and 621 of the lower polarizing plate protective films 616 and 620 areset to 0°, an alignment control direction 608 of the upper opticallyanisotropic layer 607 is 270°, and an alignment control direction 615 ofthe lower optically anisotropic layer 614 is 180° (0°-90° attachment).

(Manufacture of Optical Compensation Sheet)

(Manufacture of Celluloseacetate Film)

A celluloseacetate solution is prepared by heating and agitating thefollowing compositions put into a mixing tank and dissolving componentsof the compositions.

Composition of Celluloseacetate Solution

Celluloseacetate having acidity of 60.7 to 61.1% 100 parts by weightTriphenylphosphate (plasticizer) 7.8 parts by weightBiphenyldiphenylphosphate (plasticizer) 3.9 parts by weightMethylenechloride (first solvent) 336 parts by weight Methanol (secondsolvent) 29 parts by weight 1-buthanol (third solvent) 11 parts byweight

A retardation enhancement solution is prepared by inputting thefollowing retardation enhancer of 16 parts by weight, methylene chlorideof 92 parts by weight and methanol of 8 parts by weight into a differentmixing tank, heating and agitating them. A dope is prepared by mixing acelluloseacetate solution of 474 parts by weight with a retardationenhancement solution of 25 parts by weight and sufficiently agitatingthem. The addition amount of the retardation enhancer is 6.0 parts byweight for celluloseacetate of 100 parts by weight.

Retardation Enhancer

The obtained dope is expanded using a band expander. A celluloseacetatefilm (80 μm thick) having remaining solvent of 0.3 wt % is prepared bydrying a film on a band with warm wind of 70° C. after the temperatureof the film surface reaches 40° C. and then again drying the film withdrying wind of 140° C. Re and Rth retardation values for a wavelength of546 nm are measured for the prepared celluloseacetate film (transparentsupport and transparent protective film) using an ellipsometer (M-150available from JASCO Corporation). As a result of the measurement, Re is8 nm and Rth is 78 nm. The prepared celluloseacetate film is digestedinto a potassium hydroxide solution (25° C.) of 2.0 N for two minutes,neutralized with sulfuric acid, washed with pure water, and then dried.In this manner, the celluloseacetate film for the transparent protectivefilm is manufactured.

(Manufacture of Alignment Film for Optically Anisotropic Film)

An application solution having the following compositions is applied onthe celluloseacetate film using a #16 wire bar coater. The applicationsolution is dried for 60 seconds with warm wind of 60° C., and thenagain for 150 seconds with warm wind of 90° C. Next, the formed film issubjected to a rubbing treatment in the same direction as an in-planeretardation axis (in parallel to an expansion direction) of thecelluloseacetate film (accordingly, the alignment control direction(rubbing direction of the optically anisotropic layer is in parallel tothe retardation axis of the celluloseacetate film).

Composition of Alignment Film Application Solution

Following modified polyvinylalcohol 20 parts by weight Water 360 partsby weight Methanol 120 parts by weight Glutaraldehyde (plasticizer) 1.0parts by weightModified Polyvinylalcohol

(Manufacture of Optically Anisotropic Film)

On the alignment film is applied an application solution in which thefollowing discotic liquid crystal compound of 91.0 g, ethyleneoxidemodified trimethylolpropanetriacrylate (V#360 available from OSAKAORGANIC CHEMICAL INDUSTRY LTD.) of 9.0 g, celluloseacetatebutylate(CAB551-0.2 available from Eastman Chemical Company) of 2.0 g,celluloseacetatebutylate (CAB531-1 available from Eastman ChemicalCompany) of 0.5 g, photopolymerization initiator (IRGACURE 907 availablefrom Nihon Ciba-Geigy K.K.) of 3.0 g, intensifier (KAYACURE DETXavailable from Nippon Kayaku Co., Ltd) of 1.0 g, andfluoroaliphatic-containing copolymer (Megaface F780 Dainippon InkCorporation) of 1.3 g are dissolved into methylethylketone of 207 g, at6.2 ml/m² using a #3.6 wire bar. This application solution is heated fortwo minutes in a constant temperature zone of 130° C. to align thediscotic liquid crystal compound. Next, the discotic liquid crystalcompound is polymerized by means of UV radiation for one minute attemperature of 60° C. using a high pressure mercury lamp of 120 W/cm.Thereafter, the temperature decreases to a room temperature. Thus, theoptically anisotropic layer is formed and the optical compensation sheetis manufactured.

Liquid Crystal Compound

When the polarizing plate is in cross Nicol arrangement, no spot isobserved in the obtained optical compensation sheet when viewed in thefront and a direction inclined by 60° from a normal.

<<Manufacture of (Elliptical) Polarizing Plate>>

A polarizer is manufactured by absorbing iodine into an expandedpolyvinylalcohol film, and the manufactured optical compensation sheetis laminated on one side of the polarizer at a support plane using apolyvinylalcohol adhesive. In addition, a 80 μm thickcellulosetriacetate film (TD-80U available from FUJIFILM Corporation) issubjected to a saponification treatment, and is laminated on a sideopposite to the liquid crystal cell of the polarizer using apolyvinylalcohol adhesive. The absorption axis of the polarizer and theretardation axis (in parallel to the expansion direction) of the supportof the optical compensation film are arranged in parallel to each other(accordingly, the absorption axis of the polarizer is in parallel to thealignment control direction of the optically anisotropic layer). Thepolarizing plate is so cut that its long or short side is in parallel tothe retardation axis of the support. In this manner, the ellipticalpolarizing plate is manufactured.

<<Manufacture of Liquid Crystal Display>>

The manufactured elliptical polarizing plate is laminated on an observerside surface of the manufactured TN liquid crystal cell and a backlightside surface of the liquid crystal cell, respectively, by means of anadhesive, in such a manner that optical compensation sheets of thepolarizing plates face the liquid crystal cell and absorption axes ofthe polarizers are perpendicular and in parallel to a horizontaldirection of a screen of the display device. At this time, with theabsorption axis of the polarizer of the polarizing plate and thealignment control direction of the optical compensation sheet adjustedto be in parallel to the alignment control direction (rubbing directionof the substrates) of the liquid crystal cell, the liquid crystaldisplay is manufactured.

(Optical Measurement of Manufactured Liquid Crystal Display)

A rectangular wave voltage of 60 Hz is applied to the manufacturedliquid crystal display in a normally white mode with white display of1.5V and black display of 5V. A transmittance ratio CR (whitedisplay/black display) is measured using a measuring instrument(EZ-Contrast 160D available from ELDIM Corporation). A front CR of 1000(contrast ratio: 1000 vs. 1) is obtained. After the manufactured liquidcrystal display is stored in a test room in temperature 40° humidity 80%environments and then is left alone for one hour at a room temperature,a black display luminance difference between a panel center and a centerof a long side end portion of the polarizing plate is measured to be 0.1cd/m². No light leakage out of a circumference of the polarizing plateis observed by naked eyes. In addition, a viewing angle giving a CR of10 or more is 80° in the left and 90° in the left.

Comparative Reference Example 7-1

The conventional liquid crystal display shown in FIG. 31 ismanufactured. The reference example 7-1 has the same configuration asReference example 7-1, except that every angle is rotated by −45° in acounterclockwise direction.

After the manufactured liquid crystal display is stored in a test roomin temperature 40° humidity 80% environments and then is left alone forone hour at a room temperature, a black display luminance differencebetween a panel center and a center of a long side end portion of thepolarizing plate is measured to be 0.5 cd/m². Light leakage on acircular arc at long and short sides of a circumference of thepolarizing plate is observed by naked eyes. In addition, a viewing anglegiving a CR of more than 10 is 80° in the left and 80° in the left.

Example Comparative Example

An optical simulation is performed for the liquid crystal display shownin FIG. 32 to confirm the effect of the invention. An LCD Master Ver6.11(available from Shintech Corporation) is used for optical calculation.The liquid crystal cell, the electrodes, the substrates, the polarizingplates and so on may be used as conventional for the liquid crystaldisplay. ZLI-4792 attached to the LCD Master is used as a liquid crystalmaterial. The liquid crystal cell is set to be a TN mode and a twistangle is set to be 90°. An alignment direction at a backlight side isset to be 315°, and an alignment direction at a display plane side isset to be 45°. A liquid crystal material having positive dielectricanisotropy has retardation (that is, the product (Δn·d_(LC)) of thethickness d_(LC) (μm) of the liquid crystal layer and the refractiveindex anisotropy Δn) of 400 nm. A liquid crystal application voltage is1.8 V in the white display and 5.6 in the black display. G1220DUattached to the LCD Master is used for the polarizer. A backlightattached to the LCD Master is used as a light source. With thisconfiguration, an optical characteristic of the liquid crystal displayshown in FIG. 32 is calculated by the LCD Master.

Example 7-1 Comparative Example 7-1

An optical characteristic of the liquid crystal display shown in FIG. 2having a configuration and specification that the liquid crystal layerhas the same arrangement as in the conventional liquid crystal display(FIG. 31), the polarizer absorption axis is rotated by +45° for 0°-90°attachment, and the alignment control direction of the opticallyanisotropic layer is rotated by +20° to intersect the alignment axis ofthe substrate is calculated by the LCD Master.

An absorption axis angle of the polarizing plate is 0° at a backlightside and 90° at a display plane side (0°-90° attachment), and thealignment control direction of the optically anisotropic layer is 155°at a backlight side and 245° at a display plane side (intersection angleθ=20°).

When Re and Rth of the polarizing plate protective film are 10 nm and 90nm, respectively, a CR viewing angle is 80° in the left and 80° in theright, showing substantially bilateral symmetry, and a luminancedifference between left and right sides at a polar angle of 60° in blackdisplay is 0.0035 (cd/m²).

Table 4 shows CR values calculated in a polar angle 60° inclineddirection while varying Re and Rth of the polarizing plate protectivefilm.

TABLE 4 RETARDATION OF PROTECTIVE FILM CR AT POLAR ANGLE OF 60° Re RthRe + 2x RIGHT LEFT LEFT RIGHT (nm) (nm) Rth ≦ 280 UPPER UPPER LOWERUPPER EXAMPLE 7-1-1 20 20 O 60 x 3 x 10 O 14 x 8 EXAMPLE 7-1-2 20 50 O120 x 8 O 42 O 27 O 25 EXAMPLE 7-1-3 20 80 O 180 O 22 O 121 O 17 O 102EXAMPLE 7-1-4 20 100 O 220 O 28 O 26 x 10 O 50 EXAMPLE 7-1-5 20 120 O260 O 16 x 10 x 6 O 18 EXAMPLE 7-1-6 50 20 O 90 x 4 O 15 O 28 O 13EXAMPLE 7-1-7 50 50 O 150 x 8 O 43 O 52 O 74 EXAMPLE 7-1-8 50 80 O 210 O11 O 21 O 18 O 257 EXAMPLE 7-1-9 80 20 O 120 x 4 O 16 O 82 O 21 EXAMPLE7-1-10 80 50 O 180 x 6 O 17 O 84 O 108 EXAMPLE 7-1-11 80 80 O 240 x 5 x7 O 16 O 44 EXAMPLE 7-1-12 120 20 O 160 x 4 x 9 O 493 O 21 EXAMPLE7-1-13 120 50 O 220 x 3 x 6 O 41 O 22 EXAMPLE 7-1-14 120 80 O 280 x 3 x3 O 10 O 11 EXAMPLE 7-1-15 150 20 O 190 x 3 x 5 O 81 O 13 EXAMPLE 7-1-16150 50 O 250 x 2 x 3 O 20 x 10 EXAMPLE 7-1-17 200 20 O 240 x 2 x 3 O 16x 5 COMPARATIVE 20 150 x 320 x 6 x 4 x 3 x 6 EXAMPLE 7-1-1 COMPARATIVE20 200 x 420 x 2 x 1 x 1 x 2 EXAMPLE 7-1-2 COMPARATIVE 80 120 x 320 x 3x 2 x 4 x 9 EXAMPLE 7-1-3 COMPARATIVE 80 150 x 380 x 2 x 1 x 2 x 4EXAMPLE 7-1-4 COMPARATIVE 80 200 x 480 x 1 x 1 x 1 x 2 EXAMPLE 7-1-5COMPARATIVE 120 120 x 360 x 2 x 1 x 3 x 5 EXAMPLE 7-1-6 COMPARATIVE 15080 x 310 x 2 x 2 x 7 x 6 EXAMPLE 7-1-7 COMPARATIVE 200 50 x 300 x 1 x 2x 8 x 4 EXAMPLE 7-1-8 COMPARATIVE 200 80 x 360 x 1 x 1 x 5 x 3 EXAMPLE7-1-9 COMPARATIVE 200 120 x 440 x 1 x 1 x 2 x 2 EXAMPLE 7-1-10COMPARATIVE 200 200 x 600 x 0 x 0 x 1 x 1 EXAMPLE 7-1-11 COMPARATIVE 25020 x 290 x 1 x 2 x 8 x 3 EXAMPLE 7-1-12 COMPARATIVE 250 50 x 350 x 1 x 1x 5 x 2 EXAMPLE 7-1-13 COMPARATIVE 250 80 x 410 x 1 x 1 x 3 x 1 EXAMPLE7-1-14 COMPARATIVE 250 120 x 490 x 1 x 1 x 2 x 1 EXAMPLE 7-1-15COMPARATIVE 250 200 x 650 x 0 x 0 x 1 x 0 EXAMPLE 7-1-16

Example 7-2 Comparative Example 7-2

An optical characteristic of the liquid crystal display shown in FIG. 2having a configuration and specification that the liquid crystal layerhas the same arrangement as in the conventional liquid crystal display(FIG. 31), the polarizer absorption axis is rotated by +45° for 0°-90°attachment, and the alignment control direction of the opticallyanisotropic layer is rotated by +15° to intersect the alignment axis ofthe substrate is calculated by the LCD Master.

An absorption axis angle of the polarizing plate is 0° at a backlightside and 90° at a display plane side (0°-90° attachment), and thealignment control direction of the optically anisotropic layer is 150°at a backlight side and 240° at a display plane side (intersection angleθ=15°).

When Re and Rth of the polarizing plate protective film are 10 nm and 90nm, respectively, a CR viewing angle is 80° in the left and 80° in theright, showing substantially bilateral symmetry, and a luminancedifference between left and right sides at a polar angle of 60° in blackdisplay is 0.0028 (cd/m²).

Table 5 shows CR values calculated in a polar angle 60° inclineddirection while varying Re and Rth of the polarizing plate protectivefilm.

TABLE 5 RETARDATION OF PROTECTIVE FILM CR AT POLAR ANGLE OF 60° Re RthRe + 2x RIGHT LEFT LEFT RIGHT (nm) (nm) Rth ≦ 280 UPPER UPPER LOWERUPPER EXAMPLE 7-2-1 20 20 O 60 x 4 x 10 O 14 x 9 EXAMPLE 7-2-2 20 50 O120 O 11 O 48 O 24 O 30 EXAMPLE 7-2-3 20 80 O 180 O 85 O 135 O 16 O 62EXAMPLE 7-2-4 20 100 O 220 O 76 O 24 x 9 O 28 EXAMPLE 7-2-5 20 120 O 260O 18 x 9 x 6 O 12 EXAMPLE 7-2-6 50 20 O 90 x 5 O 16 O 26 O 17 EXAMPLE7-2-7 50 50 O 150 O 15 O 108 O 45 O 121 EXAMPLE 7-2-8 50 80 O 210 O 25 O32 O 17 O 98 EXAMPLE 7-2-9 80 20 O 120 x 6 O 22 O 72 O 31 EXAMPLE 7-2-1080 50 O 180 O 11 O 32 O 74 O 318 EXAMPLE 7-2-11 80 80 O 240 x 9 O 10 O15 O 38 EXAMPLE 7-2-12 120 20 O 160 x 5 O 13 O 592 O 35 EXAMPLE 7-2-13120 50 O 220 x 5 x 8 O 43 O 31 EXAMPLE 7-2-14 120 80 O 280 x 3 x 4 O 10O 12 EXAMPLE 7-2-15 150 20 O 190 x 4 x 7 O 94 O 18 EXAMPLE 7-2-16 150 50O 250 x 3 x 4 O 21 x 12 EXAMPLE 7-2-17 200 20 O 240 x 2 x 3 O 17 x 7COMPARATIVE 20 150 x 320 x 5 x 4 x 3 x 5 EXAMPLE 7-2-1 COMPARATIVE 20200 x 420 x 2 x 1 x 1 x 2 EXAMPLE 7-2-2 COMPARATIVE 80 120 x 320 x 4 x 2x 4 x 7 EXAMPLE 7-2-3 COMPARATIVE 80 150 x 380 x 2 x 1 x 2 x 4 EXAMPLE7-2-4 COMPARATIVE 80 200 x 480 x 1 x 1 x 1 x 2 EXAMPLE 7-2-5 COMPARATIVE120 120 x 360 x 2 x 1 x 3 x 5 EXAMPLE 7-2-6 COMPARATIVE 150 80 x 310 x 2x 2 x 7 x 7 EXAMPLE 7-2-7 COMPARATIVE 200 50 x 300 x 2 x 2 x 9 x 5EXAMPLE 7-2-8 COMPARATIVE 200 80 x 360 x 1 x 1 x 5 x 3 EXAMPLE 7-2-9COMPARATIVE 200 120 x 440 x 1 x 1 x 2 x 2 EXAMPLE 7-2-10 COMPARATIVE 200200 x 600 x 0 x 0 x 1 x 1 EXAMPLE 7-2-11 COMPARATIVE 250 20 x 290 x 1 x2 x 8 x 3 EXAMPLE 7-2-12 COMPARATIVE 250 50 x 350 x 1 x 1 x 5 x 2EXAMPLE 7-2-13 COMPARATIVE 250 80 x 410 x 1 x 1 x 3 x 2 EXAMPLE 7-2-14COMPARATIVE 250 120 x 490 x 1 x 1 x 2 x 1 EXAMPLE 7-2-15 COMPARATIVE 250200 x 650 x 0 x 0 x 1 x 1 EXAMPLE 7-2-16

FIG. 35 shows a graph 1 plotting for Table 4 of Example 7-1 andComparative example 7-1. In the graph, ⊚ indicates 3 or 4 directionshaving a CR ratio of more than 10, O indicates 1 or 2 directions havinga CR ratio of more than 10, and x indicates no direction having a CRratio of more than 10. Although Example 7-2 and Comparative example 7-2are plotted, its graph is omitted since it has the same form as thegraph for Example 7-1 and Comparative example 7-1.

Example 7-3

An experiment on an actual film and panel is carried out.

Outline of device configuration is as shown in FIG. 32 showing Example7-1, and CR values are measured for a panel on which several polarizingplate protective films having different retardations are laminated.

Specifically, a liquid crystal cell is prepared as in Comparativereference example, and 5 kinds of celluloseacetate films having Re andRth values shown in the following Table 6, which are obtained byadjusting an expansion method or the kind or addition amount ofretardation controlling agent, are used instead of the celluloseacetatefilms used in the reference examples. In addition, elliptical polarizingplates and liquid crystal panels are manufactured in the same way as inthe reference examples, except that axes or directions of various filmshave relationships shown in FIGS. 32 and 33 (intersection angle θ=20°).CR values at a polar angle 60° inclined direction are measured for themanufactured liquid crystal panels by means of EZ-Contrast 160D.

Results of the measurement are shown in Table 6 and graph 2 of FIG. 36.

TABLE 6 RETARDATION OF PROTECTIVE FILM CR AT POLAR ANGLE 60° Re Rth Re +2x RIGHT LEFT LEFT RIGHT (nm) (nm) Rth ≦ 280 UPPER UPPER LOWER UPPEREXAMPLE 7-3-1 5 90 O 185 O 39 O 130 O 13 O 51 EXAMPLE 7-3-2 10 130 O 270O 16 x 8 x 5 O 13 EXAMPLE 7-3-3 30 120 O 270 O 11 x 8 x 6 O 17 EXAMPLE7-3-4 35 140 x 315 x 5 x 4 x 3 x 8 EXAMPLE 7-3-5 50 200 x 450 x 1 x 1 x1 x 2

CONCLUSION

From the above calculation and experiment, it can be seen that a CRviewing angle in an inclined direction is large when Re and Rth of apolarizing plate protective film fall within a proper range representedby a relationship of “Re+2×Rth≦280”.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the described embodiments ofthe invention without departing from the spirit or scope of theinvention. Thus, it is intended that the invention cover allmodifications and variations of this invention consistent with the scopeof the appended claims and their equivalents.

The present application claims foreign priority based on Japanese PatentApplication Nos. JP2006-52473, JP2006-71427, JP2006-76164, JP2006-80397,JP2006-81977, JP2006-88235 and JP2006-318486 filed Feb. 28, Mar. 15,Mar. 20, Mar. 23, Mar. 24, Mar. 28 and Nov. 27 of 2006, respectively,the contents of which are incorporated herein by reference.

1. A liquid crystal display comprising: a pair of polarizing plates,each comprising a polarizer and a transparent layer, transmission axesof the pair of polarizing plates being perpendicular to each other; anda liquid crystal panel between the pair of polarizing plates, whereinthe liquid crystal panel comprises a pair of substrates disposedopposite to each other, one of the pair of substrates having anelectrode on one side thereof, a liquid crystal layer including liquidcrystal molecules aligned by alignment axes of opposite surfaces of thepair of substrates, and a pair of optically anisotropic layers, theliquid crystal layer being between the pair of optically anisotropiclayers wherein the liquid crystal panel has a double symmetrical axiswith respect to a cubic structure defined by: upper and lower alignmentcontrol directions of the liquid crystal layer which are defined by thealignment axes of opposite surfaces of the pair of substrates; andalignment control directions of the pair of optically anisotropiclayers, the double symmetrical axis being parallel to the surfaces ofthe pair of substrates, a transmission axis of one of the pair ofpolarizing plates is parallel to the double symmetrical axis, and atransmission axis of the other of the pair of polarizing plates isperpendicular to the double symmetrical axis, and wherein thetransparent layer between the liquid crystal layer and the polarizer isa biaxial retardation layer, and an in-plane retardation axisperpendicular to an absorption axis of the polarizer closer to thebiaxial retardation layer.
 2. The liquid crystal display according toclaim 1, wherein the biaxial retardation layer has an NZ value of 0.1 to0.4, wherein Nz=(nx−nz)/(nx−ny), nx represents a refractive index in aretardation axis direction in plane, ny represents a refractive index ina direction perpendicular to nx in plane, and nz represents a refractiveindex in a direction perpendicular to nx and ny.
 3. The liquid crystaldisplay according to claim 1, wherein the biaxial retardation layer hasan in-plane retardation of 20 to 80 nm.
 4. The liquid crystal displayaccording to claim 1, wherein the biaxial retardation layer has anin-plane retardation of 0 to 70 nm.
 5. The liquid crystal displayaccording to claim 1, wherein at least one of the polarizing platesfurther comprises a light diffusion layer, wherein the light diffusionlayer comprises a translucent resin and translucent particles having arefractive index different from that of the translucent resin, and thelight diffusion layer has an internal haze of 45 to 80%.
 6. The liquidcrystal display according to claim 1, wherein one of the pair ofpolarizing plates includes a retardation layer, and the retardationlayer is disposed between the polarizer of the one of the pair ofpolarizing plates and the liquid crystal panel.